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                                                                    EXHIBIT 4(o)





                       WILLIAMS HOLDINGS OF DELAWARE, INC.





                          THE WILLIAMS COMPANIES, INC.





                                       AND





                                 CITIBANK, N.A.



                                     TRUSTEE







                          FIRST SUPPLEMENTAL INDENTURE



                            DATED AS OF JULY 31, 1999




                     SUPPLEMENTING THE INDENTURE DATED AS OF
                                FEBRUARY 1, 1996





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                          FIRST SUPPLEMENTAL INDENTURE


         FIRST SUPPLEMENTAL INDENTURE (the "First Supplemental Indenture"),
dated as of July 31, 1999, by and among Williams Holdings of Delaware, Inc.
("WHD"), a Delaware corporation, The Williams Companies, Inc. ("TWC"), a
Delaware corporation, and Citibank, N.A., as Trustee (the "Trustee").

                                   WITNESSETH:

         WHEREAS, WHD and the Trustee entered into an Indenture dated as of
February 1, 1996 (the "Indenture"), pursuant to which Indenture WHD has issued
certain 6 1/4% Senior Debentures due 2006 and Medium-Term Notes (6.40%-6.91%)
due 1999-2002 (collectively, the "Notes"); and

         WHEREAS, pursuant to an Agreement and Plan of Merger dated as of July
31, 1999, by and between WHD and TWC, WHD has been merged into TWC; and

         WHEREAS, Section 9.1 of the Indenture permits the Trustee and WHD to
enter into indentures supplemental to evidence succession of another person to
WHD and the assumption by such successor of the covenants and obligations of WHD
under the Indenture.

         NOW, THEREFORE, for and in consideration of the premises and the mutual
covenants contained herein and in the Indenture and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged,
WHD, TWC, and the Trustee hereby agree as follows:

         Section 1. Definitions. Capitalized terms, which are used but not
defined herein, shall have the meanings ascribed to such terms in the Indenture.

         Section 2. Assumption of Certain Obligations.

         (a) TWC hereby expressly assumes (i) the due and punctual payment of
the principal of, premium, if any, on, interest on, and any additional amounts
payable under the Indenture in respect of, the Notes, and (ii) the performance
of all of the covenants provided for in the Indenture to be performed or
observed by WHD.

         (b) WHD and the Trustee hereby acknowledge that TWC shall succeed to,
and be substituted for, and may exercise every right and power of, WHD under the
Indenture with the same effect as if TWC had been named therein.

         Section 3. Effect of First Supplemental Indenture. From and after the
execution and delivery of this First Supplemental Indenture, the Indenture shall
be deemed to be modified as herein provided, but except as modified hereby, the
Indenture
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shall continue in full force and effect. The Indenture as modified hereby shall
be read, taken, and construed as one and the same instrument.

         Section 4. Notice. Any notice or communication by the Trustee to TWC is
duly given if in writing and delivered in person or by express mail service to
the address set forth below:

                           The Williams Companies, Inc.
                           One Williams Center
                           Tulsa, Oklahoma  74172
                           Attention:   Treasurer

         Section 5. Governing Law. This First Supplemental Indenture shall be
governed by and construed in accordance with the laws of the State of New York
(regardless of the laws that might otherwise govern under applicable principles
of conflicts of laws) as to all matters, including, without limitation, matters
of validity, construction, effect, performance, and remedies.

         Section 6. Counterparts. This First Supplemental Indenture may be
executed in any number of counterparts, each of which, when so executed and
delivered, shall be an original, but such counterparts shall together constitute
but one and the same instrument.

         IN WITNESS WHEREOF, each of WHD, TWC, and the Trustee has caused this
First Supplemental Indenture to be executed on its behalf by its duly authorized
officer and has caused its official seal to be impressed hereon and attested by
one of its duly authorized officers, all as of the day and year first above
written.

[SEAL]                              WILLIAMS HOLDINGS OF DELAWARE, INC.

Attest

/s/ SHAWNA L. GEHRES                By: /s/ JAMES G. IVEY
------------------------------         ----------------------------------------
Name:  Shawna L. Gehres             Name:  James G. Ivey
Title: Secretary                    Title: Treasurer


[SEAL]                              THE WILLIAMS COMPANIES, INC.

Attest

/s/ SHAWNA L. GEHRES                By: /s/ JAMES G. IVEY
------------------------------         ----------------------------------------
Name:  Shawna L. Gehres             Name:  James G. Ivey
Title: Secretary                    Title: Treasurer





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[SEAL]                              CITIBANK, N.A., AS TRUSTEE

Attest

/s/ NANCY FORTE                     By: /s/ WAFAA ORFY
------------------------------         ----------------------------------------
Name:    Nancy Forte                Name:    Wafaa Orfy
Title:   Trust Officer              Title:   Assistant Vice President