EXHIBIT 5

                           [UNION PACIFIC LETTERHEAD]

                                                                    June 7, 2001

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 Sirs:

   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 The Chase Manhattan Bank
(Citibank, N.A. and The Chase Manhattan 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