There are 59 national parks in the United States and they are all celebrating the 100th birthday of the National Park Service. On August 25, 1916, President Woodrow Wilson signed an act of Congress, the National Park Service Organic Act, which created the agency that now watches over 84.4 million acres of land, 4.5 million acres of oceans, reservoirs and lakes, 85,000 miles of rivers and streams, and 43,000 miles of shoreline.