John C. Frémont traveled into the Las Vegas Valley on May 3, 1844, while it was still part of Mexico. He was appointed by President John Tyler to lead a group of scientists, scouts, and spies for the United States Army Corps of Engineers who were preparing for a possible war with Mexico. Upon arriving in the valley they made camp at the Las Vegas Springs, establishing a clandestine fort there. A war with Mexico did occur, resulting in the region becoming United States territory. The fort was used in later years by travelers, mountain men, hunters, and traders seeking shelter, but was never permanently inhabited.