FIRST AMENDMENT TO REVOLVING CREDIT AGREEMENT

Exhibit 10.21

FIRST AMENDMENT TO REVOLVING CREDIT AGREEMENT

THIS FIRST AMENDMENT TO REVOLVING CREDIT AGREEMENT (the “Amendment”) is dated this the 7th  day of August, 2007 by and among DELTIC TIMBER CORPORATION, a Delaware corporation (the “Borrower”) and SUNTRUST BANK, JPMORGAN CHASE BANK, N.A., AMERICAN AGCREDIT, PCA, COOPERATIVE CENTRALE RAIFFEISEN-BOERENLEENBANK, B.A., “RABOBANK NEDERLAND,” NEW YORK BRANCH, WELLS FARGO BANK, N.A., REGIONS BANK (for itself and as successor to AmSouth Bank), BANCORPSOUTH BANK (collectively the “Lenders”), and SUNTRUST BANK, in its capacity as Issuing Bank, Swingline Lender and Administrative Agent (the “Administrative Agent”) for the Lenders.

RECITALS:

A. The Borrower, the Lenders, the Administrative Agent, the Swingline Lender and the Issuing Bank entered into a Revolving Credit Agreement dated as of September 9, 2005 (the “ Credit Agreement ”).

B. Pursuant to Section 2.24 of the Credit Agreement concerning “Increase of Revolving Commitments; Additional Lenders,” the Borrower previously increased the Aggregate Revolving Commitments to $300,000,000.

C. As of the date of this Amendment, the Revolving Commitments of the Lenders are as follows:

D. The Borrower, the Lenders, the Administrative Agent, the Swingline Lender and the Issuing Bank desire to amend the Credit Agreement to: (i) reinstate the facility under Section 2.24 of the Credit Agreement, allowing the Borrower the option to request an increase of the Aggregate Revolving Commitments to an amount not exceeding $350,000,000; and (ii) to make the other amendments as set forth herein.

E. Terms not defined herein shall have the meanings ascribed to such terms in the Credit Agreement.

NOW, THEREFORE, in consideration of the premises and for other good and valuable consideration, the receipt and adequacy of which is hereby acknowledged, the parties hereto agree as follows:

1. Amended Definitions and Additional Definitions . Section 1.1 of the Credit Agreement concerning “Definitions” is amended by adding the following additional definitions in the appropriate alphabetical order:

“ Acquisition ” shall mean (a) any Investment by the Borrower or any of its Subsidiaries in any other Person pursuant to which such Person shall become a Subsidiary of the Borrower or any of its Subsidiaries or shall be merged with the Borrower or any of its Subsidiaries or (b) any acquisition by the Borrower or any of its Subsidiaries of the assets of any Person (other than an existing Subsidiary of the Borrower) which constitutes all or substantially all of the assets of such Person or which comprises a business unit of such Person.

“ Pro Forma Basis ” means, for purposes of calculating compliance with respect to a proposed Acquisition, that such transaction shall be deemed to have occurred as of the first day of the four fiscal-quarter period ending as of the most recent fiscal quarter end preceding the effective date of such Acquisition. For purposes of any such calculation in respect of any Acquisition as referred to in Section 7.4(g) : (a) any Indebtedness incurred or assumed in connection with such transaction which is not retired in connection with such transaction (i) shall be deemed to have been incurred as of the first day of the applicable period, and (ii) if such Indebtedness has a floating or formula rate, shall have an implied rate of interest for the applicable period for purposes of this definition determined by utilizing the rate which is or would be in effect with respect to such Indebtedness as at the relevant date of determination; (b) income statement items (whether positive or negative) and capital expenditures attributable to the Person or property acquired in such Acquisition, shall be included beginning as of the first day of the applicable period; and (c) pro forma adjustments may be included to the extent that such adjustments are calculated in a manner not inconsistent with GAAP and would give effect to events that are: (y) directly attributable to such transaction and (z) expected to have a continuing impact on the Borrower and its Subsidiaries.

“ Pro Forma Compliance Certificate ” means a certificate of a Responsible Officer of the Borrower delivered to the Administrative Agent in connection with any Acquisition referred to in Section 7.4(g) , which shall contain a reasonably detailed calculation of compliance with the ratio requirements of Section 7.4(g) , upon giving effect to the applicable transaction on a Pro Forma Basis, as of the most recent fiscal quarter end preceding the date of the applicable Acquisition.

Section 1.1 of the Credit Agreement is amended by adding the following provision at the

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end of the definition of Consolidated EBITDA:

Consolidated EBITDA shall include EBITDA on a Pro Forma Basis with respect to any Acquisition, annualized from the date of such Acquisition for a period not to exceed four fiscal quarters, so long as the calculation thereof is done in a manner reasonably calculated to comply with GAAP, and such calculation is detailed in the supporting calculations to a covenant compliance certificate as detailed and measured to the Administrative Agent’s reasonable satisfaction.

Section 1.1 of the Credit Agreement is amended by adding the following provision at the end of the definition of Consolidated Net Income:

Consolidated Net Income shall include the net income (or loss) on a Pro Forma Basis with respect to any Acquisition, annualized from the date of such Acquisition for a period not to exceed four fiscal quarters, so long as the calculation thereof is done in a manner reasonably calculated to comply with GAAP, and such calculation is detailed in the supporting calculations to a covenant compliance certificate as detailed and measured to the Administrative Agent’s reasonable satisfaction.

The definition of Aggregate Commitment Amount set forth in Section 1.1 of the Credit Agreement is amended to reflect that as of August 7th, 2007, the Aggregate Revolving Commitment Amount is $300,000,000.

2. Extension of Commitment Termination Date . Section 1.1 of the Credit Agreement is amended by deleting the definition of “Revolving Commitment Termination Date,” or “Commitment Termination Date,” and the following is substituted in lieu thereof:

“ Revolving Commitment Termination Date ,” or “ Commitment Termination Date ” shall mean the earliest of (i) September 9, 2012, (ii) the date on which the Revolving Commitments are terminated pursuant to Section 2.8 and (iii) the date on which all amounts outstanding under this Agreement have been declared or have automatically become due and payable (whether by acceleration or otherwise).

3. Amendment to Pricing . Section 1.1 of the Credit Agreement concerning “Applicable Commitment Fee Percentage” and “Applicable Margin” are amended so that references to Schedule I after the effective date of this Amendment, shall refer to the amended Schedule I, attached hereto and incorporated herein by reference. All other references in the Credit Agreement to Schedule I shall hereafter refer to amended Schedule I attached to this Amendment.

4. Reinstatement of Accordion Facility . Section 2.24 of the Credit Agreement concerning “Increase of Revolver Commitments; Additional Lenders,” is amended so that all references therein to $300,000,000, shall be amended to an amount equal to $350,000,000.

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5. Amendment to Leverage Ratio Covenant . Section 6.1 of the Credit Agreement concerning “Leverage Ratio” is amended by deleting such section and inserting the following in lieu thereof:

Section 6.1 Leverage Ratio . The Borrower and its Subsidiaries shall maintain as of the last day of each fiscal quarter of the Borrower, a Leverage Ratio of not greater than 0.65:1.0, commencing with the th