The prototype was built in 1899 as the “Thomas S. Bullock” for the West Side Flume & Lumber Company. It served as a mainline and logging engine on both the WSF&L and Hetch Hetchy & Yosemite Valley railroad. The #3 was converted to standard gauge in 1947. In 1962, the locomotive was sold to the Roaring Camp & Big Trees Railroad in Felton, California as their #2 and converted back to 3-foot gauge. The Heisler is still in operation today!