Rocky Mountain Arsenal National Wildlife Refuge, located in Commerce City, Colo., is the largest refuge in the National Wildlife System in the U.S. Nowhere else can you get the vastness of open prairie with views of the Front Range and the Denver skyline. And the refuge is loaded with a wide variety of wildlife to boot. The eastern plains of Colorado used to have thousands of bison roaming the open prairie. Today most of the bison in Colorado are on private land or managed in small herds by the U.S. Fish and Wildlife Service. A herd of just under 100 lives at Rocky Mountain Arsenal National Wildlife Refuge thanks to a successful reintroduction program.