Jefferson County, Jefferson Territory

Jefferson County was a county of the extralegal United States Territory of Jefferson that existed from November 28, 1859, until February 28, 1861. Its territory covered a broad swath surrounding the region of the Pike's Peak Gold Rush, and was a functioning democratically elected government until the organization of the Territory of Colorado in 1861. At that time, the successor Jefferson County was permanently created, taking its name from its predecessor and incorporating the heart of its territory.

In July 1858, gold was discovered along the South Platte River in Arapahoe County, Kansas Territory. This discovery precipitated the Pike's Peak Gold Rush. Many residents of the mining region felt disconnected from the remote territorial governments of Kansas and Nebraska, so they voted to form their own Territory of Jefferson on October 24, 1859. On November 28, the General Assembly of the Territory of Jefferson organized 12 counties: Arrappahoe County, Cheyenne County, El Paso County, Fountain County, Heele County, Jackson County, Jefferson County, Mountain County, North County, Park County, Saratoga County, and St. Vrain's County.

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