The locomotive collection of the California State Railroad Museum contains 19 steam locomotives dating from 1862 to 1944. The Museum's locomotives illustrate the development of steam technology from its early years in the mid-nineteenth century through its apogee and climax in the 1940s. The engines range in size from the diminutive Southern Pacific No. 1, "C.P. Huntington," (the Museum's logo locomotive) to the million-pound giant, Southern Pacific articulated cab-forward No. 4294. Fewer than 30 full-size steam locomotives built prior to 1880 exist in the United States. The Museum has five of these, including Central Pacific Railroad locomotive No. 1, "Gov. Stanford."

The Museum's collection also contains 19 first and second-generation internal combustion locomotives. Early gasoline-fueled motor cars, such as the Museum's Nevada Copper Belt No. 21, "Yerington," paved the way for the diesel locomotive in the mid-twentieth century. This technology revolutionized railroading. From Southern Pacific E-9 No. 6501, painted in vibrant "Daylight" colors, to Atchison, Topeka & Santa Fe Railway F7A and B Nos. 347C and B, painted in the "Warbonnet" attire they wore while pulling the Super Chief, to workaday switch engines and the unique Krauss-Maffei diesel-hydraulic locomotive, the Museum's diesels reflect the development of modern railroad motive power.

While the locomotive collection of the California State Railroad Museum is extensive, only a portion is on public exhibition at any one time. The remaining engines are either undergoing restoration or awaiting restoration in the Museum's shop facilities.