In 1938, the Atlantic Coast Line had Baldwin build twelve 4-8-4 Class R-1 locomotives, also known as Class 1800 because of their numbers, for express train service between Richmond, Virginia and Jacksonville, Florida. Their design was considered very successful and the boiler in particular exceeded many expectations. They pulled 1,500-ton trains of 20 cars and were even able to accelerate them significantly faster than the manufacturer had initially calculated.

Of note, the direct heating area of the actual firebox was increased from 272 square feet to 568 square feet  using a combustion chamber and thermic syphons. The back pressure of the cylinders was also very low, especially in the upper speed range, and allowed greater power output. The only known problem concerned the mass balancing, which was initially calculated incorrectly by Baldwin and still had to be improved.

After the adjustments to the mass balancing, the locomotives were approved for 90 mph and are said to have regularly reached 100 mph. When they later had to pull express freight trains, the maximum train load was set at 6,200 tons. Their service ended between 1951 and 1952.