Theodore Roosevelt National Park is located in Billings and McKenzie counties in Wyoming, Gallatin and Park counties in the state of North Dakota, United States.
As stated in the foundation document:
Theodore Roosevelt National Park memorializes Theodore Roosevelt and pays tribute to his enduring contribution to the conservation of our nation’s resources by preserving and protecting the scenery, wildlife, and wilderness qualities of the North Dakota Badlands—the landscape that inspired Roosevelt and still inspires visitors today.