Glacier

Declared in 1910, largely thanks to promotion by the Great Northern Railway, which built luxurious Swiss-style hotels to draw well-off tourists. In 1932 it was formally joined with Canada's Waterton Lakes National Park to form the Waterton-Glacier International Peace Park, the first of its kind in the world and a symbol of cross-border friendship and cooperation between the United States and Canada; since 1995 the two parks have shared a joint UNESCO World Heritage listing. The park is named for the more than 25 glaciers that still survive in its mountains, though their number has fallen sharply since the 19th century as the ice has retreated with climate change — to the point that the park's own scientists expect them to be all but gone within decades.