Lewis and Clark Caverns in Montana is a three thousand-acre state park known for its limestone cave, visitor facilities, and hiking trails. Although the Lewis and Clark Expedition camped nearby in 1805, they never entered the cavern; its name reflects the cave’s overlook above a long stretch of their Jefferson River route. Local ranchers brought the cave to wider attention in the 1890s, and it was developed for tours before becoming a national monument in the early twentieth century. After losing federal status in 1937, it passed to Montana as the state’s first state park. The caverns were formed in ancient Madison Limestone and still shelter Townsend’s big-eared bats.