The following important events in the history of Colorado affected political boundaries, record keeping, and family movements.
1803: The United States acquired the sections of Colorado north and east of the Arkansas River as part of the Louisiana Purchase. Beginning in 1806 government expeditions were sent to map the area, and fur trappers and traders followed in the 1820s. Western settlers in the 1840s and 1850s bypassed Colorado on their way to the Pacific Coast.
1848: The United States acquired the rest of present-day Colorado from Mexico.
1851: Hispanic families from New Mexico founded San Luis, the oldest continually occupied town in Colorado.
1854: The Colorado area was divided politically among the territories of Kansas, Nebraska, Utah, and New Mexico.
1858: Denver and other mining towns were organized by Colorado's early gold seekers. In 1858 the miners also organized Arapahoe County of Kansas Territory.
1859: Colorado pioneers created what they called Jefferson Territory without the sanction of Congress. It was to have included all of present-day Colorado and some areas of Utah and Wyoming.
1861: Congress organized the Colorado Territory. The first seventeen counties were organized the same year.
1870: Railroad links between Denver and Cheyenne and between Denver and Kansas City connected Colorado with the east and west coasts.
1876: Colorado became a state.
1881: Western Colorado was officially opened to white settlement after most of the Ute Indians had been moved to reservations in Utah.
1890: Colorado's population exceeded 400,000 when the last major gold strike was made at Cripple Creek.
An especially helpful source for studying the history of Colorado is LeRoy R. Hafen, ed., Colorado and Its People: A Narrative and Topical History of the Centennial State, Four Volumes. (New York, NY: Lewis Historical Publishing Co., 1948; FHL book 978.8 H2h; film 1000143). Volumes 3-4 contain personal and family histories.
A bibliography of local histories is found in Bohdan S. Wynar and Roberta J. Depp, eds., Colorado Bibliography (Littleton, Colorado: Libraries Unlimited, 1980; FHL book 978.8 A3c, pages 53-92).