The National Park Service turns 100 today, and it’s come a long way in 100 years.

The first national park, Yellowstone, was actually founded in 1872, with other national parks added periodically after that. By 1916, there were 35 national parks, but no central group to maintain them. President Woodrow Wilson created the National Park Service in 1916, and since then it has grown from protecting 35 national parks, to protecting 412 designated areas covering 84 million acres.

Over 300 million people visit national parks every year, from the largest, Wrangell-St. Elias National Park and Preserve in Alaska, which covers 13.2 million acres, to the smallest, Thaddeus Kosciuszko National Memorial in Pennsylvania, which covers a grand total of 0.02 acres (it’s a house).

The birthday wishes are starting to roll in from around the country, including a Google Doodle, and a quick video greeting from Oprah Winfrey:

In addition to special events around the country, the National Park Service is celebrating its birthday by making entrances to all national parks free of charge between August 25 and August 28.