USP Florence ADMAX, better known as ADX Florence or the "Alcatraz of the Rockies," is the federal Bureau of Prisons' only administrative-maximum facility and is widely regarded as the most secure prison in the country. The idea for a facility like this took shape after two correctional officers were killed at USP Marion in Illinois in 1983, an event that convinced BOP leadership a dedicated, ultra-secure "control unit" prison was needed for the system's most dangerous or high-risk inmates. Construction finished in 1994 at a cost of roughly $60 million, and the prison began receiving inmates that same year, becoming fully operational in early 1995. It sits within the larger Florence correctional complex in Fremont County, Colorado, about 100 miles south of Denver, on a roughly 37-acre secured footprint ringed by razor wire, motion sensors, and remote-controlled steel doors. It can hold up to 474 men, though it has generally run below that number, and most inmates spend the bulk of their day alone in reinforced concrete cells under close supervision. Its population has long included some of the country's most notorious offenders, which has made the facility a frequent subject of press coverage and public curiosity.