Happy birthday to the National Park Service!

Friday marks 101 years since President Woodrow Wilson created the agency, which aims to preserve and celebrate America’s great outdoors.

2016 was its best year yet. The National Park Service welcomed 331 million visitors for its centennial year, which was a 7.7 percent increase over 2015.

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The NPS oversees more than 400 parks. Just 59 of the sites are designated as national parks.

Browse the photo gallery below to see which national parks were the 10 most visited in 2016.