The papers of Weldon B. Heyburn span the years 1889 to 1911, with the bulk of the material covering the years 1892 to 1903. They consist primarily of Heyburn's correspondence in his capacity of lawyer for mining companies, respected Republican politician, and as U.S. Senator from Idaho. Included are both incoming and outgoing correspondence, letterpress books containing copies of outgoing letters, a scrapbook, a book containing his Senate accomplishments, and legal briefs for cases in which he represented one of the parties. Also included is one year of correspondence belonging to LeRoi Mining and Smelting Co. of Rossland, British Columbia.

In addition to this manuscript group the Special Collections division of the University of Idaho Library also has a printed book of memorial addresses presented in the U.S. House of Representatives and Senate upon the occasion of the death of Senator Heyburn, and a Master's thesis which deals with the political career of the Senator through his first term in the Senate, 1909.