The first execution in Colorado occurred in 1859 with the hanging of John Stoefel for murder. In the ensuing years, many people, all men and all convicted of murder, were executed but in 1967, after the execution of Luis Jose Monge, the death penalty in Colorado, although still on the books, was no longer actively pursued. A few years later, in the 1972 case of Furman v. Georgia, 408 U.S. 238, the United States Supreme Court determined that most death penalty laws in America, including Colorado's, were unconstitutional because they violated the Constitution's ban against cruel and unusual punishment.
In 1976, Colorado's new death penalty laws passed constitutional muster although since that time Colorado has only executed one person, Gary Lee Davis, who was executed in 1997, thirty years after Colorado's last execution. There are currently three people on Colorado's death row - Nathan Dunlap, Sir Mario Owens and Robert Ray. It should be noted that, although the population of Colorado is only 4% African-American, all three people on Colorado's death row are African-Americans.
Currently in the United States, 31 states have death penalty statutes and 19, plus the District of Columbia, have abolished it. In the states that still have the death penalty, 12 of them, including Colorado, have not executed anyone in the last 5 years. A recent Pew Research Center poll found that support for the death penalty in America is reaching an all-time low and is still declining.
For an in-depth look at the history of the death penalty in Colorado, please see Professor Michael Radelet's article CAPITAL PUNISHMENT IN COLORADO: 1859-1972.