President Woodrow Wilson signed the National Park Service Organic Act into law on the 25th of August 1916. This document created a new federal agency within the Department of the Interior to manage America's growing collection of protected lands.
Business magnate Stephen Mather led the campaign that made the agency possible and became the first director of the newly formed NPS. He worked alongside journalist Robert Sterling Yard to publish articles praising the scenic and historic qualities of these places.
The largest unit in the system is Wrangell, St. Elias National Park and Preserve in Alaska covering 13,200,000 acres. This single area represents over 16 percent of the entire National Park System.
The Great American Outdoors Act reduced this backlog by $9.5 billion over five years beginning in fiscal year 2021. The act was signed on the 4th of August 2020 after the agency faced an estimated $12 billion maintenance backlog in 2019.
In January 2022 the agency adopted the Resist Accept Direct framework to address intensifying global change. It became part of an NPS policy memorandum titled Managing National Parks in an Era of Climate Change.
During the October 2025 government shutdown the Interior Department directed that over four hundred NPS units remain partially open while furloughing approximately nine thousand two hundred to nine thousand three hundred employees. This represented about two-thirds of total staff with only limited excepted personnel like law enforcement and emergency responders staying on duty.