Indenture

EXHIBIT 4.1

THIS SECURITY IS AN UNSECURED SENIOR DEBT OBLIGATION OF ZIONS BANCORPORATION. THIS SECURITY IS NOT A DEPOSIT OR SAVINGS ACCOUNT AND IS NOT INSURED BY THE FEDERAL DEPOSIT INSURANCE CORPORATION OR ANY OTHER GOVERNMENTAL AGENCY OR INSTRUMENTALITY.

THIS SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY OR A NOMINEE THEREOF. THIS SECURITY MAY NOT BE EXCHANGED IN WHOLE OR IN PART FOR A SECURITY REGISTERED, AND NO TRANSFER OF THIS SECURITY IN WHOLE OR IN PART MAY BE REGISTERED, IN THE NAME OF ANY PERSON OTHER THAN SUCH DEPOSITARY OR A NOMINEE THEREOF, EXCEPT IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE.

UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”), TO ZIONS BANCORPORATION, OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

ZIONS BANCORPORATION

Floating Rate Senior Notes due December 10, 2009

ZIONS BANCORPORATION, a corporation duly organized and existing under the laws of the State of Utah (herein called the “Company,” which term includes any successor Person under the Indenture hereinafter referred to), for value received, hereby promises to pay to Cede & Co., or registered assigns, the principal sum of Two Hundred Ninety-Five Million Six Hundred Thirty Thousand Dollars ($295,630,000) on December 10, 2009, and to pay interest thereon from December 11, 2007 or from the most recent Interest Payment Date to which interest has been paid or duly provided for, quarterly on March 10, June 10, September 10 and December 10 in each year (each such date, an “Interest Payment Date”), commencing March 10, 2008. Interest will accrue at the Floating Interest Rate (as defined below), until the principal hereof is paid or made available for payment. Any premium and any such installment of interest that is overdue at any time shall also bear interest (to the extent that the payment of such interest shall be legally enforceable), at the rate per annum at which the principal then bears interest, from the date any such overdue amount first becomes due until it is paid or made available for payment. Notwithstanding the foregoing, interest on any principal, premium or installment of interest that is overdue shall be payable on demand. The interest so payable, and punctually paid or duly provided for, on any Interest Payment Date will, as provided in such Indenture, be paid to the Person in whose name this Security (or one or more Predecessor Securities) is registered at the close of business on the Regular Record Date for such interest, which shall be the March 1, June 1, September 1 or December 1 (whether or not a Business Day), as the case may be, immediately preceding such Interest Payment Date. Any such interest not so punctually paid or duly provided for will forthwith cease to be payable to the Holder on such Regular Record Date and may either be paid to the Person in whose name this Security (or one or more Predecessor Securities) is registered at the close of business on a Special Record Date for the payment of such Defaulted Interest to be fixed by the Trustee, notice whereof shall be given to Holders of Securities of this series not less than 10 days prior to such Special Record Date, or be paid at any time in any other lawful manner not inconsistent with the requirements of any securities exchange on which the Securities of this series may be listed, and upon such notice as may be required by such exchange, all as more fully provided in said Indenture.

The Floating Interest Rate shall be, for each Interest Period (as defined below), a per annum rate in effect for each day of such Interest Period equal to LIBOR (as defined below) plus 150 basis points, as determined by the Calculation Agent (as defined below). The Floating Interest Rate for each Interest Period will be set quarterly on the first day of each Interest Period commencing December 11, 2007 (each such date, an “Interest Reset Date”). The amount of interest for each day that this Security is outstanding (the “Daily Interest Amount”) shall be calculated by dividing the interest rate in effect for that day by 360 and multiplying the result by the outstanding principal amount of this Security. The amount of interest to be paid on this Security for each Interest Period shall be calculated by adding the Daily Interest Amount for each day in such Interest Period.

In the event that an Interest Payment Date is not a Business Day, interest will be paid on the next day that is a Business Day, with the same force and effect as if made on the Interest Payment Date, and without any interest or other payment with respect to the delay. If the date of Stated Maturity for the principal falls on a day that is not a Business Day, the payment of the principal amount of this Security will be made on the next succeeding Business Day and no interest will accrue for the period from and after such date of Stated Maturity. If any Interest Reset Date for the Security falls on a day that is not a Business Day, the Interest Reset Date will be postponed to the next day that is a Business Day; if that

Business Day is in the next succeeding calendar month, the Interest Reset Date will be the immediately preceding Business Day. “Business Day,” with respect to this Security, is a Monday, Tuesday, Wednesday, Thursday or Friday that is not a day on which banking institutions in Salt Lake City, Utah or New York City, New York generally are authorized or required by law or executive order to close, that is also a London Business Day (as defined below).

“Calculation Agent” means any Person authorized by the Company to calculate the relevant rate of interest to be paid on this Security on behalf of the Company. The calculation agent is initially Zions Direct, Inc. until such time as the Company appoints a successor calculation agent.

“London Business Day” is any day in which dealings in United States dollars are transacted or, with respect to any future date, are expected to be transacted in the London interbank market.

“LIBOR,” with respect to any Interest Period, shall be the rate (expressed as a percentage per annum) for deposits in United States dollars for a three-month period beginning on the relevant Interest Reset Date that appears on Reuters Page LIBOR01 (as defined below) as of 11:00 a.m., London time, on the Determination Date. If Reuters Page LIBOR01 does not include this rate or is unavailable on the Determination Date, the Calculation Agent will request the principal London office of each of four major banks in the London interbank market, as selected by the Calculation Agent, to provide that bank’s offered quotation (expressed as a percentage per annum) as of approximately 11:00 a.m., London time, on the Determination Date to prime banks in the London interbank market for deposits in a Representative Amount (as defined below) in United States dollars for a three-month period beginning on the first day of the applicable Interest Period. If at least two offered quotations are so provided, LIBOR for the Interest Period will be the arithmetic mean of those quotations. If fewer than two quotations are so provided, the Calculation Agent will request each of three major banks in New York City, as selected by the Calculation Agent, to provide that bank’s rate (expressed as a percentage per annum), as of approximately 11:00 a.m., New York City time, on the Determination Date for loans in a Representative Amount in United States dollars to leading European banks for a three-month period beginning on the first day of the applicable Interest Period. If at least two rates are so provided, LIBOR for the Interest Period will be the arithmetic mean of those rates. If fewer than two rates are so provided, then LIBOR for the Interest Period will be LIBOR in effect with respect to the immediately preceding Interest Period.

“Determination Date” with respect to an Interest Period shall be the second London Business Day preceding the Interest Reset Date. For the first interest period, the determinatio