Susan B. Barnes

Special for USA TODAY

2016 marks the centennial of the National Park Service, the mission of which is to preserve “unimpaired the natural and cultural resources and values of the National Park System for the enjoyment, education, and inspiration of this and future generations. The Park Service cooperates with partners to extend the benefits of natural and cultural resource conservation and outdoor recreation throughout this country and the world.”

And though we’re celebrating 100 years of the National Park System this year, from Maine to Hawaii, Florida to Alaska, and everywhere in between, not to mention American Samoa, Guam, Puerto Rico and the Virgin Islands, it may come as a surprise to learn that the first National Park was designated in 1871, 45 years before the National Park Service as we know it came into existence in 1916.

Before the National Park Service

According to The National Parks: Shaping the System, published by the National Park Service, the idea of land being preserved for everyone to enjoy was first expressed in 1832 (that’s just 56 years after the birth of United States of America in 1776) and is credited to artist George Catlin. During a trip to the Dakota region in 1832, Catlin, best known for his paintings of Native Americans, pondered the impact the western expansion would have upon these civilizations, the wildlife and the wilderness. He wrote that they might be preserved “by some great protecting policy of government…in a magnificent park…a nation’s park, containing man and beast, in all the wild(ness) and freshness of their nature’s beauty.”

Though Catlin’s idea was seemingly impractical at the time and “had no immediate effect,” just 32 years later the “national park idea came to partial fruition in 1864” when President Abraham Lincoln signed an act of Congress to transfer the federally-owned Yosemite Valley and nearby Mariposa Big Tree Grove to the State of California on condition that they would “be held for public use, resort, and recreation…inalienable for all time.”

Yosemite was cited as a precedence when Senate Public Lands Committee Chairman Samuel C. Pomeroy of Kansas presented a park legislation bill in December 1871 to protect the Yellowstone region, keeping it in federal custody and unavailable for development. President Ulysses S. Grant signed Pomeroy’s bill into law on March 1, 1872 and Yellowstone National Park, the world’s first national park, was established.

Once Yellowstone was protected, the preservation ball really started rolling: In 1875, an act of Congress made most of Michigan’s Mackinac Island a national park before it was transferred back to the state in 1895 and maintained as a state park; Sequoia, General Grant (incorporated into Kings Canyon National Park in 1940) and Yosemite became national parks in 1890 (Yosemite Valley and Mariposa Grove incorporated into Yosemite National Park in 1906); Mount Rainier joined the national parks in 1899, and a slew of other national parks followed and were established through 1916: Crater Lake (Oregon, 1902), Wind Cave (South Dakota, 1903), Mesa Verde (Colorado, 1906), Glacier (Montana, 1910), Rocky Mountain (Colorado, 1915) and Hawaii (1916, split into Haleakalä and Hawaii in 1960, and redesignated Hawai’i Volcanoes in 1961).

Spectacular national park photos from @USInterior on Instagram

The National Park Service is born

On August 25, 1916 President Woodrow Wilson signed a bill into law to create the National Park Service to oversee the already-established national parks and “such other national parks and reservations of like character as may be hereafter created by Congress.” The NPS was also directed “to conserve the scenery and the natural and historic objects and the wild life therein and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations.”

Today, more than 20,000 men and women employed with the National Park Service, alongside 221,000 volunteers, continue the charge and share “a passion for caring for the nation's special places and sharing their stories” - all 412 national parks, monuments, battlefields, military parks, historical parks, historic sites, lakeshores, seashores, recreation areas, scenic rivers and trails, and the White House.

In 2015, 307.2 million people visited the national parks, and it wouldn’t come as any surprise if that number is surpassed in 2016. The National Park Service’s Find Your Park initiative encourages everyone to find the park nearest them and share their own stories, this year and for years to come.

This weekend, in celebration of its 100th birthday, the National Park Service invites visitors to celebrateith free admission to all 412 national park sites August 25-28. And check out these fun birthday events scheduled throughout the country.

In honor of the National Park Service's 100th anniversay, USA TODAY has focused on twenty of the best-known national parks in a weekly series. See below for each park covered for guides, photo galleries, videos and more:

Acadia National Park | Arches National Park | Black Canyon of the Gunnison National Park | Death Valley National Park | Everglades National Park | Glacier National Park | Grand Canyon National Park | Grand Teton National Park | Great Sand Dunes National Park | Great Smoky Mountains National Park | Isle Royale National Park | Joshua Tree National Park | Mesa Verde National Park | Mount Rainier National Park | Olympic National Park | Rocky Mountain National Park | Sequoia & Kings Canyon National Parks | Yellowstone National Park | Yosemite National Park | Zion National Park