Between Denver and Como, US 285 mostly follows the route of the Denver, South Park and Pacific Railroad, part of the original narrow gauge transcontinental railroad. The route skirts the south side of the Mount Evans massif, then descends into and crosses the South Park. Como in Colorado's South Park still houses one of the few remaining narrow gauge roundhouses. The transcontinental railroad route breaks away from US 285 at Como, going northwest over Boreas Pass en route to Breckenridge, the historically rich gold fields of Leadville, and eventually connecting to California.