The Central Pacific Railroad number 173 was a 4-4-0 steam locomotive built by Norris-Lancaster for the Western Pacific Railroad in 1864. After its acquisition by Central Pacific, 173 was involved in a bad wreck, lying idle for two years before undergoing a sweeping reconstruction by the line's Sacramento Shops. It subsequently became the prototype for the railroad's engines when the CP began constructing locomotives. The engine was successful, and more engines were built to 173's design.