The Provisional Government of the Territory of Jefferson was an extralegal and unrecognized United States territory that existed in the Pike's Peak mining region from October 24, 1859, until it yielded to the new Territory of Colorado on June 6, 1861. The Jefferson Territory, named for Founding Father and third United States president Thomas Jefferson, included land officially part of the Kansas Territory, the Nebraska Territory, the New Mexico Territory, the Utah Territory, and the Washington Territory, but the region was remote from the governments of those five territories.

The Territory of Colorado was an organized incorporated territory of the United States that existed from February 28, 1861, until August 1, 1876, when it was admitted to the Union as the State of Colorado.