Glacier National Park
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Why to go now: In 1850, Montana's Glacier National Park had 150 glaciers, a number that has dwindled to just 25 today. In about 15 years, glacier recession models predict none will remain. And while the park is famous for retaining nearly all of its native plant and animal species – including the grizzly bear – the ecosystem could change dramatically when the glacier-fed cold water is gone. Also, arguably the park's chief tourist draw, the glaciers, will be gone, and, of course, the park's own name will become a misnomer.

How to get there: The trip to Glacier National Park is a scenic 150-mile road trip from Missoula, Montana. Visitors can also fly into Glacier Park International Airport and drive or shuttle the 30 miles to the park's West Entrance. Glacier is open year-round, but the majority of the facilities are only open during the official season – late May to early September.