Even before the United States acquired California after the Mexican–American War (1846–48), many heading for California used the isthmus crossing in preference to the long and dangerous wagon route across the vast plains and rugged mountain ranges. Discovery of gold in 1848 increased traffic greatly. In 1847 a group of New York City financiers organized the Panama Railroad Company. This company secured an exclusive concession from Colombia allowing construction of a crossing, which might be by road, rail, river, or a combination. After surveys, a railroad was chosen, and a new contract so specifying was obtained in 1850. The railroad track followed generally the line of the present canal. The first through train from the Atlantic to the Pacific side ran on the completed track on January 28, 1855.