To cite sources: >> On March 1, 1872, President Ulysses S. Grant signed The Act of Dedication law that created Yellowstone National Park. https://en.m.wikipedi

To cite sources: >> On March 1, 1872, President Ulysses S. Grant signed The Act of Dedication law that created Yellowstone National Park. https://en.m.wikipedia.org/wiki/Yellowstone_National_Park#History https://en.m.wikipedia.org/wiki/Yellowstone_National_Park#Hi... I believe the Yellowstone claim is based on the fact that it was the first park explicitly declared for the benefit of the public by a federal government.