Montana County was a county of the United States Territory of Kansas that existed from February 2, 1859 to January 29, 1861, when Kansas joined the Union as a state.
In July 1858, gold was discovered along the South Platte River in Arapahoe County of the Territory of Kansas (now in the State of Colorado). This discovery precipitating the Pike's Peak Gold Rush. To provide local government for the gold mining region, the Kansas Territorial Legislature split Arapahoe County into six counties on 1859-02-07: a much smaller Arapahoe County, Broderick County, El Paso County, Fremont County, Montana County, and Oro County. Montana County was named for the Spanish language name for the Front Range. Montana County included the fledgling gold camps of Denver City, Golden City, and Central City. None of these six counties were ever organized. Many residents of the mining region felt disconnected from the territorial government, and they formed their own Territory of Jefferson on October 24, 1859.