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Pennsylvania class L1s
United States | 1914 | 574 produced
No. 520 on display in 1993 at the Pennsylvania Railroad Museum in Strasburg
No. 520 on display in 1993 at the Pennsylvania Railroad Museum in Strasburg
Sean Lamb

The PRR's L1s class was a Mikado that received the same boiler as the K4s class Pacific. Despite the great performance of this boiler with the Belpaire firebox, these locomotives were not equipped with a stoker ex works and many of them were not retrofitted later. They were considered very successful all-rounders and, apart from the USRA designs and after the PRR class I1s, achieved the second largest number of any class of steam locomotives built for an American railway company.

Locomotive Magazine, November 1914

A total of 344 were built at the PRR's Juniata shops in Altoona, 205 at Baldwin and 25 at Lima. However, it was not long before they were replaced in some roles by 2-10-0 and 4-8-2 locomotives. In the 1930s, many were also put into storage due to the economic crisis and the electrification of an important line. These came back into the picture during World War II when their services were urgently needed. Number 520 still exists today and is on display at the Railroad Museum of Pennsylvania in Strasburg.

ManufacturerAltoona, Baldwin, Lima
Axle config2-8-2 (Mikado) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase36 ft 4 1/2 in
Fixed wheelbase17 ft 0 1/2 in
Total wheelbase72 ft 3 in
Service weight315,000 lbs
Adhesive weight238,000 lbs
Total weight473,000 lbs
Axle load59,000 lbs
Water capacity7,000 us gal
Fuel capacity25,000 lbs (coal)
Power sourcesteam
Estimated power3,100 hp (2,312 kW)
Optimal speed32 mph
Starting effort61,465 lbf
Power Plant
Driver diameter62 in
Boiler pressure205 psi
Expansion typesimple
Cylinderstwo, 27 x 30 in
Grate area70 sq ft
Firebox area301.5 sq ft
Tube heating area3,733.5 sq ft
Evaporative heating area4,035 sq ft
Superheater area1,154 sq ft
Total heating area5,189 sq ft
Calculated Values
steam locomotive
last changed: 11/2023

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