US transport organization, founded by Henry Wells, William C. Fargo, and associates in 1852 to operate between New York and California. Wells and Fargo established a monopoly west of the Mississippi within a decade, succeeding the Pony Express as the agency for transporting bullion to eastern markets, and for 20 years dominated the postal service in the West. In 1918 it merged with a number of other concerns to become the American Railway Express Company.