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. The legislation that created St. Vrain's County declared: That the territory comprised within the following limits, be erected into a county called St. Vrain's: commencing in the main channel of the south fork of the Platte River, where the 104th meridian of west longitude crosses the same, thence up the main channel of said stream to the mouth of the Cache la Poudre, thence up the main channel of the Cache la Poudre to the east line of Heele county, thence south to the 40th parallel of north latitude; thence east on said parallel to the 104th meridian of west longitude, thence north on said meridian to the place of beginning. St. Vrain's County was named in honor of
Ceran de Hault de Lassus de St. Vrain, the
French trader who established the first
trading post on the upper
South Platte River. St. Vrain's County encompassed much of what is today
Weld County, Colorado. The Jefferson Territory never received federal sanction, but on February 28, 1861,
U.S. President James Buchanan signed an act organizing the
Territory of Colorado. On November 1, 1861, the
Colorado General Assembly organized 17 counties, including
Weld County, for the new Colorado Territory. ==Elections and elected officials==