On August 25, 1916, President Woodrow Wilson signed the 'Organic Act' creating the National Park Service, a federal bureau in the Department of the Interior responsible for maintaining national parks and monuments that were then managed by the department. The National Park System has since expanded to 419 units (often referred to as parks), more than 150 related areas, and numerous programs that assist in conserving the nation's natural and cultural heritage for the benefit of current and future generations. Missisquoi and Trout National Wild and Scenic River, Vermont.