Cumberland Gap National Historical Park became a National Park in 1940. 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 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 route for the settlement of the interior of the nation. In 1750 Dr. Thomas Walker found the Gap and mapped its location, but the French and Indian Wars closed the new frontiers. After the Treaty of Sycamore Shoals ended most Indian troubles, Daniel Boone and thirty other men marked out the Wilderness Trail from what is now Kingsport Tennessee through the Cumberland Gap to Kentucky in 1775. Before the Revolutionary War was over 12,000 people crossed into the new frontier territory. By the time Kentucky was admitted into the Union, over 100,000 people had passed through the Gap. By 1800 the Gap was being used for transportation and commerce, both east and west. The Cumberland Gap was also the scene of considerable activity during the Civil War because it was of such strategic Importance. The Confederate soldiers anticipated a Union invasion through the Gap it was well fortified. In September 1861, Confederate Gen. Stephenson's troops forced the Union back into the Gap. When the Union learned of the Confederate plan, they were issued orders to retreat. Retrieving supplies stored in caves along the way, anything the troops couldn't carry was stock-piled and ready to be set afire. The explosion and subsequent wall of fire checked the Confederate advance and provided for a successful Union retreat. Today the Cumberland Gap is the main local route North and South, via Cumberland Gap Parkway (Hwy. 25E). By the mid 1990's a four lane tunnel under the Gap opened a new North-South, East-West route and the Cumberland Gap was restored like the first pioneer who saw it.