Holding political offices in Wisconsin and Colorado throughout his life, Samuel G. Colley (1807–90) is best known for serving as Indian Agent for the Upper Arkansas Indian Agency from 1860 to 1865. He was responsible for managing the Cheyenne and Arapaho prior to and during the Colorado War (1863–65). His stint as Indian agent was marked by criticism and controversy.

Born on December 8, 1807, in Bedford, New Hampshire, Samuel G. Colley married Lydia Atwood in 1832. They had their first and only son, Dexter Dole Colley, on October 28 later that year. In early 1838, the Colley family joined the New England Emigrating Company and moved to Beloit, Wisconsin. From 1838 to 1860 Samuel served in various positions, including justice of the peace, highway commissioner, and member of the Rock County Board of Supervisors, contributing to the settlement of Beloit. He also served as a member of the state legislature at various times. In 1850 Colley took a year hiatus from Wisconsin to join the rest of the nation in the California Gold Rush.

In 1860 Colley left Wisconsin and Lydia to join his son on a journey to Colorado. Upon their arrival, Samuel Colley was appointed by President Abraham Lincoln as Indian agent for the Upper Arkansas Indian Agency to manage relations between the US government and the Cheyenne and Arapaho. Around that same time Samuel’s cousin William P. Dole became commissioner of Indian affairs. Colley was based at Fort Wise, which later became known as Fort Lyon.

The impact he had during his time as Indian Agent for the Upper Arkansas area is unclear. While never formally accused, Colley and his son, Dexter, allegedly stole Indian annuities—the goods and services that were to be distributed to Native Americans according to terms of a treaty—with the goal of selling them back to the Native Americans for personal profit. In this case, annuities took the form of foodstuffs and other goods distributed to the Arapaho and Cheyenne as agreed to in the Treaty of Fort Wise.

The failure to deliver the promised annuities to the tribes and the scarcity of buffalo in the winter of 1863 led to increased incidences of starvation among Native American peoples. Some contemporary witnesses believed starvation to be the impetus behind the tribal raids on American settlers at the time. In a letter to Colonel John Milton Chivington, Colley expressed the opinion that whatever the impetus behind the raids, all hostile Native American perpetrators should be punished to the full extent. On November 29, 1864, Chivington and his soldiers massacred an unarmed group of Cheyenne and Arapaho—mostly women, children, and the elderly—at Sand Creek, Colorado. Afterward, Sam and Dexter Colley both denounced the Sand Creek Massacre, which changed the nature of future interactions between the US government and Native Americans in Colorado.

Since the majority of the Cheyenne and Arapaho left the reservation, Colley resigned as Indian Agent in 1865 and returned to Beloit, Wisconsin. After Lydia’s death in 1873, he married Clarissa Barnes Boutwell (1833–1911) the following year. He served as county sheriff until 1879, when he retired to a farm outside Beloit; he lived there until his death on October 21, 1890. Colley is remembered in Colorado for his apparently ambivalent role in the buildup and aftermath of the Sand Creek Massacre, one of the state’s greatest tragedies.