Passage: Colorado Territory was officially organized by Act of Congress on February 28, 1861, out of lands previously part of the Kansas, Nebraska, Utah, and New Mexico territories. Technically the territory was open to slavery under the Dred Scott Decision of 1857, but the question was rendered moot by the impending American Civil War and the majority pro-Union sentiment in the territory. The name "Colorado" was chosen for the territory. It had been previously suggested in 1850 by Senator Henry S. Foote as a name for a state to have been created out of present-day California south of 35° 45'. To the dismay of Denverites, the town of Colorado City was designated the first territorial capital, quickly succeeded by Golden. Denver eventually became the temporary territorial capital, but was not designated the permanent capital until 1881, five years after Colorado became a state.

Question: What war started in the same year as the formation of the Colorado Territory?
American Civil War