The Santa Fe Trail was a 19th-century transportation route through central North America that connected Missouri with Santa Fe, New Mexico. Pioneered in 1822 by William Becknell, it served as a vital commercial and military highway until the introduction of the railroad to Santa Fe in 1880. At first an international trade route between the United States and Mexico, it was the 1846 U.S. invasion route of New Mexico during the Mexican–American War.