UNIT PURCHASE AGREEMENT

                                    ARTICLE I DEFINITIONS                                                                                                                                                                                                                                                                   1

                 ARTICLE II AGREEMENT TO SELL AND PURCHASE                                                                                                                                                                                                                4

                 ARTICLE III REPRESENTATIONS AND WARRANTIES OF BOARDWALK                                                                                                                                                                          7

                ARTICLE IV REPRESENTATIONS AND WARRANTIES OF THE PURCHASER                                                                                                                                                                10

                 ARTICLE V COVENANTS                                                                                                                                                                                                                                                                12

                 ARTICLE VI MISCELLANEOUS                                                                                                                                                                                                                                                     12

This UNIT PURCHASE AGREEMENT, dated as of June 23, 2009 (this “ Agreement ”), is by and between BOARDWALK PIPELINE PARTNERS, LP, a Delaware limited partnership (“ Boardwalk ”), and BOARDWALK PIPELINES HOLDING CORP., a Delaware corporation (the “ Purchaser ”).

WHEREAS, subject to the terms and conditions set forth herein, Boardwalk desires to sell and Purchaser desires to purchase 6,684,857 Common Units (the “ Units ”) from Boardwalk in accordance with the provisions of this Agreement;

WHEREAS, Boardwalk has agreed to provide the Purchaser with certain registration rights with respect to the Units acquired pursuant hereto; and

WHEREAS, the General Partner (as hereinafter defined) has indicated it intends to exercise its right to make additional capital contributions pursuant to Section 5.2(b) of the Partnership Agreement (such contribution, the “ GP 2% Contribution ”) in connection with the issuance of the Units contemplated hereby;

NOW THEREFORE, in consideration of the mutual covenants and agreements set forth herein and for good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, the parties hereby agree as follows:

Section 1.1 Definitions

.  Capitalized terms used but not defined herein have the meanings assigned to such terms in the Partnership Agreement (as hereinafter defined).  As used in this Agreement, and unless the context requires a different meaning, the following terms have the meanings indicated:

“ Affiliate ” means, with respect to any Person, any other Person that directly or indirectly through one or more intermediaries controls, is controlled by or is under common control with, the Person in question. As used herein, the term “control” means the possession, direct or indirect, of the power to direct or cause the direction of the management and policies of a Person, whether through ownership of voting securities, by contract or otherwise.

“ Agreement ” has the meaning set forth in the introductory paragraph.

“ BGL ” means Boardwalk GP, LLC, a Delaware limited liability company.

“ Boardwalk ” has the meaning set forth in the introductory paragraph.

“ Boardwalk Entity ” means Boardwalk and its Subsidiaries.

“ Business Day ” means Monday through Friday of each week, except that a legal holiday recognized as such by the government of the United States of America or the State of Kentucky shall not be regarded as a Business Day.

“ Closing ” has the meaning specified in Section 2.2 .

“ Closing Date ” has the meaning specified in Section 2.2 .

“ Commission ” means the United States Securities and Exchange Commission.

“ Common Units ” means the common units representing limited partner interests in Boardwalk.

“ Delaware LP Act ” has the meaning specified in Section 3.1 .

“ Delaware LLC Act ” has the meaning specified in Section 3.1 .

“ Exchange Act ” means the Securities Exchange Act of 1934, as amended from time to time, and the rules and regulations of the Commission promulgated thereunder.

“ General Partner ” means Boardwalk GP, LP, a Delaware limited partnership.

“ Governmental Authority ” means, with respect to a particular Person, any country, state, county, city and political subdivision in which such Person or such Person’s Property is located or that exercises valid jurisdiction over any such Person or such Person’s Property, and any court, agency, department, commission, board, bureau or instrumentality of any of them and any monetary authority that exercises valid jurisdiction over any such Person or such Person’s Property.  Unless otherwise specified, all references to Governmental Authority herein with respect to Boardwalk means a Governmental Authority having jurisdiction over Boardwalk, its Subsidiaries or any of their respective Properties.

 “ Law ” means any federal, state, local or foreign order, writ, injunction, judgment, settlement, award, decree, statute, law, rule or regulation.

“ Lien ” means any interest in Property securing an obligation owed to, or a claim by, a Person other than the owner of the Property, whether such interest is based on the common law, statute or contract, and whether such obligation or claim is fixed or contingent, and including but not limited to the lien or security interest arising from a mortgage, encumbrance, pledge, security agreement, conditional sale or trust receipt or a lease, consignment or bailment for security purposes.  For the purpose of this Agreement, a Person shall be deemed to be the owner of any Property that it has acquired or holds subject to a conditional sale agreement, or leases under a financing lease or other arrangement pursuant to which title to the Property has been retained by or vested in some other Person in a transaction intended to create a financing.

“ Material Adverse Effect ” has the meaning specified in Section 3.1 .

“ NYSE ” means The New York Stock Exchange, Inc.

“ Operative Documents ” means, collectively, this Agreement, the Registration Rights Agreement and any other agreements or instruments executed and delivered by the Parties on even date herewith or at the Closing relating to the issuance and sale of the Units, or any amendments, supplements, continuations or modifications thereto.

“ Partnership Agreement ” means the Third Amended and Restated Agreement of Limited Partnership of Boardwalk dated June 17, 2008, as amended from time to time.

“ Partnership Securities ” means any class or series of equity interest in Boardwalk (but excluding any options, rights, warrants and appreciation rights relating to an equity interest in Boardwalk), including without limitation any Common Units, Class B Units and Incentive Distribution Rights (as defined in the Partnership Agreement).

“ Person ” means an individual or a corporation, limited liability company, partnership, joint venture, trust, unincorporated organization, association, government agency or political subdivision thereof or other entity.

“ Property ” means any interest in any kind of property or asset, whether real, personal or mixed, or tangible or intangible.

“ Purchase Price ” means an amount equal to the product of the number of Units multiplied by the Unit Price.

“ Purchaser ” has the meaning set forth in the introductory paragraph.

“ Registration Rights Agreement ” means the Second Amended and Restated Registration Rights Agreement, to be entered into at the Closing, between Boardwalk and the Purchaser in the form attached hereto as Exhibit A .

“ Representatives ” of any Person means the officers, directors, managers, employees, agents, counsel, accountants, investment bankers and other representatives of such Person.

“ Securities Act ” means the Securities Act of 1933, as amended from time to time, and the rules and regulations of the Commission promulgated thereunder.

“ Subsidiary ” means, with respect to any Person, (a) a corporation of which more than 50% of the voting power of shares entitled (without regard to the occurrence of any contingency) to vote in the election of directors or other governing body of such corporation is owned, directly or indirectly, at the date of determination, by such Person, by one or more Subsidiaries of such Person or a combination thereof, (b) a partnership (whether general or limited) in which such Person or a Subsidiary of such Person is, at the date of determination, a general or limited partner of such partnership, but only if more than 50% of the partnership interests of such partnership (considering all of the partnership interests of the partnership as a single class) is owned, directly or indirectly, at the date of determination, by such Person, by one or more Subsidiaries of such Person, or a combination thereof, or (c) any other Person (other than a corporation or a partnership) in which such Person, one or more Subsidiaries of such Person, or a combination thereof, directly or indirectly, at the date of determination, has (i) at least a majority ownership interest or (ii) the power to elect or direct the election of a majority of the directors or other governing body of such Person.

“ Unitholders ” means the unitholders of Boardwalk.

“ Unit Price ” has the meaning specified in Section 2.1(b) .

“ Units ” has the meaning set forth in the recitals to this Agreement.

“ Waiver and Consent Agreement ” means the Waiver and Consent of Lender, dated as of the date hereof, between the Purchaser and Boardwalk Pipelines, LP.

Section 2.1   Sale and Purchase .

(a)   Subject to the terms and conditions hereof, Boardwalk hereby agrees to issue and sell to the Purchaser and the Purchaser hereby agrees to purchase from Boardwalk, 6,684,857 Common Units, and the Purchaser agrees to pay Boardwalk the Unit Price for each Purchased Unit as set forth in paragraph (b) below.

(b)   The amount per Unit the Purchaser will pay to Boardwalk to purchase the Units (the “ Unit Price ”) hereunder shall be $21.99.

Section 2.2   Closing

.  Subject to the terms and conditions hereof, the consummation of the purchase and sale of the Units hereunder (the “ Closing ”) shall take place at the offices of Vinson & Elkins L.L.P., 666 Fifth Avenue, 26th Floor, New York, New York on June 26, 2009 or such other date mutually agreed by the parties (the date of such closing, the “ Closing Date ”).

Section 2.3   Mutual Conditions

.  The respective obligations of each party to consummate the purchase and issuance and sale of the Units shall be subject to the satisfaction on or prior to the Closing Date of each of the following conditions (any or all of which may be waived by a party on behalf of itself in writing, in whole or in part, to the extent permitted by applicable Law):

(a)   no Law shall have been enacted or promulgated, and no action shall have been taken, by any Governmental Authority of competent jurisdiction that temporarily, preliminarily or permanently restrains, precludes, enjoins or otherwise prohibits the consummation of the transactions contemplated hereby or makes the transactions contemplated hereby illegal; and

(b)   there shall not be pending any suit, action or proceeding by any Governmental Authority seeking to restrain, preclude, enjoin or prohibit the transactions contemplated by this Agreement.

Section 2.4   The Purchaser’s Conditions .  The obligation of the Purchaser to consummate the purchase of the Units shall be subject to the satisfaction on or prior to the Closing Date of each of the following conditions (any or all of which may be waived by the Purchaser in writing, in whole or in part, to the extent permitted by applicable Law):

(a)   Boardwalk shall have performed and complied with the covenants and agreements contained in this Agreement that are required to be performed and complied with by Boardwalk on or prior to the Closing Date;

(b)   The representations and warranties of Boardwalk contained in this Agreement that are qualified by materiality or a Material Adverse Effect shall be true and correct when made and as of the Closing Date and all other representations and warranties of Boardwalk shall be true and correct in all material respects when made and as of the Closing Date, in each case as though made at and as of the Closing Date (except that representations made as of a specific date shall be required to be true and correct as of such date only);

(c)   The NYSE shall have authorized, upon official notice of issuance, the listing of the Units.

(d)   No notice of delisting from the NYSE shall have been received by Boardwalk with respect to the Common Units; and

(e)   Boardwalk shall have delivered, or caused to be delivered, to the Purchaser at the Closing, Boardwalk’s closing deliveries described in Section 2.6 .

Section 2.5   Boardwalk’s Conditions

.  The obligation of Boardwalk to consummate the sale of the Units to the Purchaser shall be subject to the satisfaction on or prior to the Closing Date of each of the following conditions with respect to the Purchaser (any or all of which may be waived by Boardwalk in writing, in whole or in part, to the extent permitted by applicable Law):

(a)   the representations and warranties of the Purchaser contained in this Agreement that are qualified by materiality shall be true and correct when made and as of the Closing Date and all other representations and warranties of the Purchaser shall be true and correct in all material respects as of the Closing Date (except that representations of the Purchaser made as of a specific date shall be required to be true and correct as of such date only);

(b)   the Purchaser shall have delivered, or caused to be delivered, to Boardwalk at the Closing the Purchaser’s closing deliveries described in Section 2.7 ; and

(c)   Boardwalk and the General Partner shall have received an opinion from Vinson & Elkins L.L.P., legal counsel to Boardwalk, dated as of the Closing, in form and substance reasonably acceptable to Boardwalk and the General Partner.

Section 2.6   Boardwalk Deliveries .  At the Closing, subject to the terms and conditions hereof, Boardwalk will deliver, or cause to be delivered, to the Purchaser:

(a)   A certificate or certificates representing the Units (bearing the legend set forth in Section 4.9 ) and meeting the requirements of the Partnership Agreement, free and clear of any Liens, other than transfer restrictions under the Partnership Agreement and applicable federal and state securities laws;

(b)   A certificate of the Secretary of State of the State of Delaware, dated a recent date, to the effect that Boardwalk is in good standing;

(c)   A cross-receipt executed by Boardwalk and delivered to the Purchaser certifying that it has received the Purchase Price from the Purchaser as of the Closing Date;

(d)   An opinion addressed to the Purchaser from Vinson & Elkins L.L.P., legal counsel to Boardwalk, dated as of the Closing, in form and substance reasonably acceptable to the Purchaser;

(e)   The Registration Rights Agreement, which shall have been duly executed by Boardwalk;

(f)   A certificate, dated the Closing Date and signed by the Chief Executive Officer and the Chief Financial Officer of BGL, in their capacities as such, stating that:

(i)   Boardwalk has performed and complied with the covenants and agreements contained in this Agreement that are required to be performed and complied with by Boardwalk on or prior to the Closing Date; and

(ii)   The representations and warranties of Boardwalk contained in this Agreement that are qualified by materiality or Material Adverse Effect are true and correct as of the Closing Date and all other representations and warranties of Boardwalk are true and correct in all material respects as of the Closing Date (except that representations made as of a specific date shall be required to be true and correct as of such date only); and

(g)   A certificate of the Secretary or Assistant Secretary of BGL, on behalf of Boardwalk, certifying as to (1) the Partnership Agreement, as amended, (2) board resolutions authorizing the execution and delivery of the Operative Documents and the consummation of the transactions contemplated thereby, including the issuance of the Units and (3) its incumbent officers authorized to execute the Operative Documents, setting forth the name and title and bearing the signatures of such officers.

Section 2.7   Purchaser Deliveries .  At the Closing, subject to the terms and conditions hereof, the Purchaser will deliver, or cause to be delivered, to Boardwalk:

(a)   Payment to Boardwalk of the Purchase Price by wire transfer of immediately available funds to an account designated by Boardwalk in writing at least two Business Days prior to the Closing Date;

(b)   The Registration Rights Agreement, which shall have been duly executed by the Purchaser;

(c)   A cross-receipt executed by the Purchaser and delivered to Boardwalk certifying that it has received the Units as of the Closing Date;

(d)   Such documents and instruments that may be required by the General Partner pursuant to Section 10.4 of the Partnership Agreement (including a properly completed Taxation Certification), which shall have been duly executed by the Purchaser; and

(e)   A certificate from the Purchaser, dated the Closing Date and signed by an appropriate officer of the Purchaser, in his or her capacity as such, stating that:

(i)   The Purchaser has performed and complied with the covenants and agreements contained in this Agreement that are required to be performed and complied with by it on or prior to the Closing Date; and

(ii)   The representations and warranties of the Purchaser contained in this Agreement that are qualified by materiality are true and correct as of the Closing Date and all other representations and warranties of the Purchaser are true and correct in all material respects as of the Closing Date (except that representations made as of a specific date shall be required to be true and correct as of such date only).

(f)   A copy of the Waiver and Consent Agreement executed by the Purchaser.

Boardwalk represents and warrants to the Purchaser as follows:

Section 3.1     Existence .  Each of the General Partner, BGL and the Boardwalk Entities has been duly formed and is validly existing and in good standing as a limited partnership under the Delaware Revised Uniform Limited Partnership Act (the “ Delaware LP Act ”) or a limited liability company under the Delaware Limited Liability Company Act (the “ Delaware LLC Act ”), as applicable, has the full partnership or limited liability company power and authority necessary to own or hold its properties and assets and to conduct the businesses in which it is engaged, and is duly registered or qualified to do business and in good standing as a foreign limited partnership or limited liability company in each jurisdiction in which its ownership or lease of property or the conduct of its business requires such qualification, except where the failure to so register or qualify could not reasonably be expected to (i) have a material adverse effect on the condition (financial or other), results of operations, securityholders’ equity, properties or business of the Boardwalk Entities taken as a whole (a “ Material Adverse Effect ”) or (ii) subject the limited partners of Boardwalk to any material liability or disability.

Section 3.2   No Conflict .  Assuming the Waiver and Consent Agreement is duly executed and delivered by the Purchaser, none of the offering, issuance and sale by Boardwalk of the Units and the application of the proceeds therefrom, the execution, delivery and performance of the Operative Documents by Boardwalk, or the consummation of the transactions contemplated hereby or thereby (i) conflicts or will conflict with, or constitutes or will constitute a violation of, the certificate or agreement of limited partnership, certificate of formation, limited liability company agreement or other organizational documents of the Boardwalk Entities, (ii) conflicts or will conflict with, or constitutes or will constitute a breach or violation of or a default under (or an event that, with notice or lapse of time or both, would constitute such a breach or violation of or default under), any indenture, mortgage, deed of trust, loan agreement, lease or other agreement or instrument to which any of the Boardwalk Entities is a party, by which any of them is bound or to which any of their respective properties or assets is subject, (iii) violates or will violate any statute, law, ordinance, regulation, order, judgment, decree or injunction of any court or governmental agency or body to which any of the Boardwalk Entities or any of their respective properties or assets may be subject or (iv) will result in the creation or imposition of any Lien upon any property or assets of any Boardwalk Entity which conflicts, breaches, violations, defaults or Liens, in the case of clauses (ii), (iii) or (iv), would, individually or in the aggregate, have a Material Adverse Effect.

Section 3.3   No Default .  None of the Boardwalk Entities (i) is in violation of its certificate or agreement of limited partnership, certificate of formation or limited liability company agreement, or other organizational documents, (ii) is in breach of or default under any term, covenant or condition contained in any indenture, mortgage, deed of trust, loan agreement, lease or other agreement or instrument to which it is a party, by which it is bound or to which any of its properties or assets is subject (and no event has occurred that, with notice or lapse of time or both, would constitute such a breach or default), (iii) is in violation of any statute, law, ordinance, rule, regulation, order, judgment, decree or injunction of any court or governmental agency or body to which it or its property or assets may be subject or (iv) has failed to obtain any license, permit, certificate, franchise or other governmental authorization or permit necessary to the ownership of its property or to the conduct of its business, except, in the case of clauses (ii) or (iv), as could not reasonably be expected to have a Material Adverse Effect.

Section 3.4   Authority .  On the Closing Date, Boardwalk will have all requisite power and authority to issue, sell and deliver the Units, in accordance with and upon the terms and conditions set forth in this Agreement and the Partnership Agreement.  On the Closing Date, all corporate, partnership or limited liability company action, as the case may be, required to be taken by the General Partner, BGL and Boardwalk for the authorization, issuance, sale and delivery of the Units, the execution and delivery of the Operative Documents and the consummation of the transactions contemplated hereby and thereby shall have been validly taken.

Section 3.5   Due Authorization .  Each of the Operative Documents has been duly and validly authorized and has been or, with respect to the Operative Documents to be delivered at the Closing Date, will be, validly executed and delivered by Boardwalk and constitutes, or will constitute, the legal, valid and binding obligations of Boardwalk, enforceable in accordance with its terms, except as such enforceability may be limited by bankruptcy, insolvency, fraudulent transfer and similar laws affecting creditors’ rights generally or by general principles of equity, including principles of commercial reasonableness, fair dealing and good faith.

Section 3.6   Valid Issuance .  The Units to be issued and sold by Boardwalk to the Purchaser hereunder have been duly authorized in accordance with the Partnership Agreement and, when issued and delivered against payment therefor pursuant to this Agreement, will be validly issued in accordance with the Partnership Agreement, fully paid (to the extent required under the Partnership Agreement) and non-assessable (except as such nonassessability may be affected by matters described in Sections 17-303, 17-607 and 17-804 of the Delaware LP Act).

Section 3.7   No Preemptive or Registration Rights .  Except as set forth in the Partnership Agreement, there are no preemptive rights or other rights to subscribe for or to purchase, nor any restriction upon the voting or transfer of, any capital stock or partnership or membership interests of any of the Boardwalk Entities, in each case pursuant to any other agreement or instrument to which any of such entities is a party or by which any one of them may be bound.  Except as contemplated by this Agreement and the Registration Rights Agreement or provided for in the Partnership Agreement, (i) neither the execution of this Agreement, nor the issuance of the Units as contemplated by this Agreement gives rise to any rights for or relating to the registration of any Partnership Securities, and (ii) there are no contracts, agreements or understandings between any Boardwalk Entity and any person granting such person the right to require Boardwalk to file a registration statement under the Securities Act with respect to any securities of Boardwalk owned or to be owned by such person, or to require Boardwalk to include such securities in any securities registered or to be registered pursuant to any registration statement filed by or required to be filed by Boardwalk under the Securities Act.

Section 3.8   Periodic Reports .  Boardwalk has filed all forms, reports, schedules and statements required to be filed by it under the Exchange Act subsequent to December 31, 2008 and when they were filed with the Commission, each such form, report, schedule and statement conformed in all material respects to the requirements of the Exchange Act and did not contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading.

Section 3.9   Litigation .  Except as described in Boardwalk’s Annual Report on Form 10-K for the year ended December 31, 2008 or any other forms, reports, schedules and statements required to be filed by it under the Exchange Act subsequent to December 31, 2008, there are no legal or governmental proceedings pending to which any Boardwalk Entity is a party or to which any property or asset of any Boardwalk Entity is subject that could reasonably be expected to have, individually or in the aggregate, a Material Adverse Effect or a material adverse effect on the performance of this Agreement or the consummation of the transactions contemplated hereby, and to the knowledge of Boardwalk, no such proceedings are threatened by Governmental Authorities or others.

Section 3.10    Certain Fees .  No fees or commissions are or will be payable by Boardwalk to brokers, finders, or investment bankers with respect to the sale of any of the Units or the consummation of the transaction contemplated by this Agreement.  Boardwalk agrees that it will indemnify and hold harmless the Purchaser from and against any and all claims, demands, or liabilities for broker’s, finder’s, placement, or other similar fees or commissions incurred by Boardwalk or alleged to have been incurred by Boardwalk in connection with the sale of the Units or the consummation of the transactions contemplated by this Agreement.

Section 3.11    No Side Agreements .  There are no agreements by, among or between Boardwalk or any of its Affiliates, on the one hand, and the Purchaser or any of its Affiliates, on the other hand, with respect to the transactions contemplated hereby other than the Operative Documents or the Waiver and Consent Agreement nor promises or inducements for future transactions between or among any of such parties.

Section 3.12    No Registration .  Assuming the accuracy of the representations and warranties of the Purchaser contained in Section 4.6   and Section 4.7 , the issuance and sale of the Units pursuant to this Agreement is exempt from registration requirements of the Securities Act of 1933, as amended.

Section 3.13    No Integration .  Neither Boardwalk nor any of its Subsidiaries have, directly or indirectly through any agent, sold, offered for sale, solicited offers to buy or otherwise negotiated in respect of, any “security” (as defined in the Securities Act of 1933, as amended) that is or will be integrated with the sale of the Units in a manner that would require registration under the Securities Act of 1933, as amended.

The Purchaser hereby represents and warrants to Boardwalk that:

Section 4.1   Existence .  The Purchaser is duly organized and validly existing and in good standing as a corporation under the laws of the State of Delaware, with all corporate power and authority to own properties and to conduct its business as currently conducted.

Section 4.2   Authorization, Enforceability .  The Purchaser has all necessary corporate power and authority to execute, deliver and perform its obligations under this Agreement, the Registration Rights Agreement and the Waiver and Consent Agreement and to consummate the transactions contemplated thereby, and the execution, delivery and performance by the Purchaser of this Agreement, the Registration Rights Agreement and the Waiver and Consent Agreement has been duly authorized by all necessary action on the part of the Purchaser; and this Agreement, the Registration Rights Agreement and the Waiver and Consent Agreement constitute the legal, valid and binding obligations of the Purchaser, enforceable in accordance with their terms, except as such enforceability may be limited by bankruptcy, insolvency, fraudulent transfer and similar laws affecting creditors’ rights generally or by ge