| Powertype: | Steam |
| P&RR C1a class | |
| Builder: | Reading Company |
| Builddate: | 1915 |
| Totalproduction: | 4 |
| Whytetype: | 4-4-4 |
| Driverdiameter: | 6feet |
| Locoweight: | 230,800 lb (104,700 kg) |
| Fueltype: | Coal |
| Cylindercount: | Two, outside |
| Cylindersize: | 23.5x |
| Boilerpressure: | 2402NaN2 |
| Tractiveeffort: | 36,604 lbf (162.82 kN) |
| Withdrawndate: | 1916 |
The C1a Class were a type of 4-4-4 steam locomotive built for the Philadelphia and Reading Railway in 1915. Four locomotives were built, road numbers #110-113. They used front and rear trucks that were effectively identical. During a year of operation, they proved to be quite unstable; after that year, they were rebuilt to 4-4-2 "Atlantic" locomotives, reclassified as P7sa, and renumbered #350-353.