The National Park Service was officially established in 1916 to protect, at that time, 35 national parks and monuments (including the very first, Yellowstone, founded in 1872).
Today, the NPS oversees 61 national parks, as well as hundreds more monuments and nationally protected lands. California has the most national parks (9), but Alaska (8) is close behind. Indiana welcomed the newest national park this year, Indiana Dunes on Lake Michigan, while Tennessee's Great Smoky Mountains National Park is the most visited.
States without a national park include Alabama, Connecticut, Delaware, Georgia, Idaho, Illinois, Iowa, Kansas, Louisiana, Maryland, Massachusetts, Mississippi, Nebraska, New Hampshire, New Jersey, New York, Oklahoma, Pennsylvania, Rhode Island, Vermont, West Virginia and Wisconsin.