The Rocky Mountain Arsenal National Wildlife Refuge is situated 30 minutes north of downtown Denver. For the second half of the 20th century, the Site was home to a US Military installation that produced most of the West's chemical weapons. Declared a superfund site, the area's environmental remediation is mostly complete. It has been handed over to the US Fish and Wildlife Service and boasts an impressive array of plant and animal species. The reserve is also home to a protected herd of American bison.