In 1937, the RF&P received its first five 4-8-4 locomotives from Baldwin. They got the numbers 551 to 555 and were named after Civil War generals from Virginia, hence the designation “Generals class”. They were very powerful, but could not reach Washington, D.C. since they had an axle load too high for the Long Bridge across the Potomac and were too wide for some tunnels. So they only stayed on the other side of the Potomac in Virginia and were almost always used in freight service.

To remedy these problems, the next locomotives were lighter and narrower. While the driver diameter and cylinder dimensions remained the same, the boiler pressure was reduced and the superheater was made much smaller. As a compensation, the firebox surface was much increased with a combustion chamber. The tender was now also smaller with a water capacity of 16,000 instead of 20,000 gallons. 

Of this lighter variant, six were built in 1938 and 1942 each. They got the numbers 601 to 612 and were named after Virginian Governors, what led to the designation “Governors class”. When still more were needed, ten were built in 1944 and 1945. These were nearly identical to the Governors, but got a bigger tender with a water capacity of 18,000 gallons. These now got the names of statesmen of Virginia and got the corresponding class name.