The 1940 United States Senate election in Wyoming took place on November 5, 1940. Democratic Senator Joseph C. O'Mahoney ran for re-election to a second full term. He faced Republican Milward Simpson, a member of the University of Wyoming Board of Trustees and a former State Representative, in the general election. Though the presidential election in Wyoming was relatively close, O'Mahoney outperformed President Franklin D. Roosevelt's narrow win, and defeated Simpson in a landslide to win his second term.
^"Newcastle Attorney Enters Campaign for Senate Seat". Casper Star-Tribune. Casper, Wyo. March 18, 1940. p. 1.
^ abcHunt, Lester C. (1941). 1941 Official Directory of Wyoming and Election Returns for 1940. Casper, Wyo.: Prairie Publishing Co. pp. 70–74.
^"Harry Henderson In Senate Race". Casper Star-Tribune. Casper, Wyo. February 29, 1940. p. 1.
^"I. W. DInsmore of Rawlins Enters Race for Senate". Casper Star-Tribune. Casper, Wyo. March 20, 1940. p. 1.
^"Saratoga Man Enters Race for U.S. Senate: R. R. Crow Is One of Five Republican Candidates; Other Filings Announced". Casper Star-Tribune. Casper, Wyo. July 22, 1940. p. 1.