Current sources attribute the name to the canyon of the Boise River near Caldwell.
However, both John Rees and Vardis Fisher believed it named for the Snake River Canyon, which forms a natural boundary for the county. The Hudson's Bay Company established Fort Boise in 1834 near what is now Parma, but abandoned it in 1855. Emigrants traveled through Canyon County on the Oregon Trail. Thomas J. Ryan, Hon. William B. Dillon, Hon.