Baddest of the badlands © Dennis Frates/Alamy
Heading west on Interstate 90, peek out the driver"s side when you"re about three-quarters of the way across South Dakota. It"s the first clue you"ve entered the Wild West: the expansive, layered landscape of Badlands National Park. It"s enjoyed government protection since 1939, first as a national monument and more completely after it was upgraded to national park status on this day in 1978. The park protects 244,000 acres of dramatically eroded bedrock replete with fossil beds—as well as the nation"s largest mixed-grass prairie, hosting bison, prairie dogs, and endangered black-footed ferrets.