The story of the first doorway to the west is commemorated at the national park, located where the borders of Tennessee, Kentucky, and Virginia meet. Carved by wind and water, Cumberland Gap forms a major break in the formidable Appalachian Mountain chain. First used by large game animals in their migratory journeys, followed by Native Americans, the Cumberland Gap was the first and best avenue for the settlement of the interior of this nation. From 1775 to 1810, the Gap's heyday, between 200,000 and 300,000 men, women, and children from all walks of life, crossed the Gap into Kentuckee. Leashed pets are permitted in the park, but are not allowed in the buildings. Leashes must be no longer than six feet.