EXHIBIT 5

                          [UNION PACIFIC LETTERHEAD]

                                                                   May 20, 2002

Union Pacific Corporation
1416 Dodge Street
Omaha, NE 68179

        Re: Union Pacific Corporation $1,000,000,000 Aggregate Public Offering
            Price of Offered Securities

Dear Ladies and Gentlemen:

   I am Senior Corporate 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 forms of Indenture
referred to in the Registration Statement (the "Indentures") between the
Company and Citibank, N.A. and the Company and JPMorgan Chase Bank formerly The
Chase Manhattan Bank, (Citibank, N.A. and JPMorgan Chase Bank, each as trustee,
the "Trustee"), pursuant to which the Debt Securities may 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 Indentures 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 and (ii) 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 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, and (ii) 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, and (ii) 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) a warrant agreement or agreements shall have been authorized,
   executed and delivered by the Company and a warrant agent, and (iii) 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 Indentures have been duly executed and delivered by the respective Trustees
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/  JAMES J. THEISEN, JR.

JJT/CAN/sla