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                                                                     EXHIBIT 5


                     [UNION PACIFIC CORPORATION LETTERHEAD]


Union Pacific Corporation
1717 Main Street
Suite 5900
Dallas, Texas 75201


                                                        May 29, 1998

     RE:  UNION PACIFIC CORPORATION $1,000,000,000 AGGREGATE PUBLIC OFFERING
          PRICE OF OFFERED SECURITIES

Dear Sirs:

     I am Assistant General Counsel of Union Pacific Corporation, a Utah
corporation (the "Company"), and I am rendering this opinion in connection with
the Company's Registration Statement on Form S-3 (the "Registration Statement")
being filed today with the Securities and Exchange Commission under the
Securities Act of 1933, as amended (the "Act"), with respect to the Company's
debt securities (the "Debt Securities"), preferred stock, with no par value
(the "Preferred Stock"), warrants to purchase Debt Securities and Preferred
Stock (the "Warrants"), and common stock, par value $2.50 per share (the
"Common Stock"), issuable upon conversion or exchange of Debt Securities or
Preferred Stock (the Debt Securities, Preferred Stock, Warrants and Common Stock
are collectively referred to as the "Offered Securities"), for issuance from
time to time pursuant to Rule 415 under the Act.

     I or attorneys under my supervision have examined the Indenture (the
"Indenture"), dated as of December 20, 1996, between the Company and Citibank,
N.A., as trustee (the "Trustee"), pursuant to which the Debt Securities will be
issued, and I have examined such other documents and made such other
investigations as I have deemed necessary or advisable for purposes of this
opinion. Based thereon, I am of the opinion that:

     1.   The Company is a corporation duly organized and validly existing
under the laws of the State of Utah.

     2.   The execution and delivery of the Indenture by the Company and the
issuance and sale of Debt Securities have been validly authorized by all
necessary corporate action by the Company.

     3.   When (i) the Registration Statement shall have become effective under
the Act, (ii) the Blue Sky or securities laws of certain states shall have been
complied with and (iii) the Debt Securities shall have been (A) duly
authorized, executed, authenticated and delivered against payment therefor or
(B) issued upon conversion or exchange of Debt Securities or

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Preferred Stock which, by their respective terms, are convertible into or
exchangeable for Debt Securities or upon exercise of Warrants, and the Company
shall have received any additional consideration which is payable upon such
conversion, exchange or exercise, the Debt Securities shall constitute binding
obligations of the Company enforceable in accordance with their terms, except as
enforceability may be limited by bankruptcy, insolvency, reorganization or other
laws relating to or affecting creditors' rights generally and subject to general
principles of equity.

     4.   When (i) the Registration Statement shall have become effective under
the Act, (ii) the Blue Sky or securities laws of certain states shall have been
complied with, and (iii) the Preferred Stock shall have been (A) authorized,
issued and sold as contemplated by the Registration Statement and the Company
shall have received consideration therefor or (B) issued upon conversion or
exchange of Debt Securities or Preferred Stock which, by their respective terms,
are convertible into or exchangeable for shares of Preferred Stock or upon
exercise of Warrants and the Company shall have received any additional
consideration which is payable upon such conversion, exchange or exercise, the
Preferred Stock will be validly issued, fully paid and non-assessable.

     5.   When (i) the Registration Statement shall have become effective under
the Act, (ii) the Blue Sky or securities laws of certain states shall have been
complied with, and (iii) the Common Stock shall have been issued upon
conversion or exchange of Debt Securities or Preferred Stock which, by their
respective terms, are convertible into or exchangeable for shares of Common
Stock, and the Company shall have received any additional consideration which
is payable upon such conversion or exchange, the Common Stock shall be validly
issued, fully paid and non-assessable.

     6.   When (i) the Registration Statement shall have become effective under
the Act, (ii) the Blue Sky or securities laws of certain states shall have been
complied with, (iii) a warrant agreement or agreements shall have been
authorized, executed and delivered by the Company and a warrant agent, and (iv)
the Warrants shall have been duly executed and delivered against payment
therefor, the Warrants shall be legally issued.

     In rendering the opinion set forth in paragraph 3 above, I have assumed
that the Indenture has been duly executed and delivered by the Trustee and duly
qualified under the Trust Indenture Act of 1939, as amended.

     I hereby consent to the filing of this opinion as an exhibit to the
Registration Statement. I also consent to the use of my name under the caption
"Legal Opinions" in the Prospectus contained in the Registration Statement.


                                        Very truly yours,
                                        
                                        /s/ Richard J. Ressler  



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