Rocky Mountain Arsenal National Wildlife Refuge is a free, roughly 16,000-acre prairie refuge just northeast of Denver where wild bison, mule deer, prairie dogs and endangered black-footed ferrets roam within sight of the city skyline.

The land has one of Colorado’s most surprising comeback stories. The U.S. Army built the Rocky Mountain Arsenal in 1942 to manufacture chemical weapons, and after decades of industrial use and a major environmental cleanup, Congress designated it a national wildlife refuge in 1992. Today the U.S. Fish and Wildlife Service manages restored shortgrass prairie, lakes and cottonwood groves that support more than 330 species of wildlife. Bison returned in 2007 when 16 animals arrived from Montana’s National Bison Range, and the herd is now one of the refuge’s biggest draws, along with raptors, white pelicans and the black-footed ferret exhibit at the Visitor Center.

Visiting is free. The refuge is open from sunrise to sunset in fall, winter and spring, and from sunrise to 8:00 p.m. between May 1 and August 1. The Visitor Center is open Wednesday through Sunday from 9:00 a.m. to 4:00 p.m. and closed on federal holidays. With 30 minutes, walk the 1-mile Discovery Trail from the Visitor Center patio or the 0.6-mile Lake Mary Loop with its boardwalk and piers over the water. Allow 45–60 minutes for the 11-mile Wildlife Drive, which has an audio tour, and two hours or more to add the Lake Ladora Loop or the Rocky Mountain Greenway Trail. Kids can earn a Junior Ranger badge. Call (303) 289-0930 with questions.

Prescribed burns are scheduled to begin Monday, October 19, 2026, and continue for several weeks, weather permitting, between 9 a.m. and 4 p.m. on up to 1,462 acres; smoke may be visible beyond the refuge. Check alerts on the Rocky Mountain Arsenal National Wildlife Refuge website for Commerce City, CO.