The Baltimore & Ohio's class Q-4 2-8-2s were erected by Baldwin Locomotive Works from 1920-1923. With 64-inch drivers, cylinder dimensions of 26x32 inches and a boiler pressure of 220 p.s.i., they developed a tractive force of 63,200 pounds. Weighing in at 298,000 pounds, they had a grate area of 70 square feet, 3819 square feet of evaporative heating surface and 955 square feet of superheating surface. With these dimensions the Q-4s were typical of the B&O's fleet of reliable, workaday freight engines that did not quite have the glamour of the larger "Big Six" 2-10-2s or the dual-service class T 4-8-2s.

It is of interest, then to note that No. 421 of class Q-4 pulled the last steam-powered passenger train of the Baltimore & Ohio on a May, 1958 run between Cleveland and Holloway, Ohio. This color view of that event, by noted rail photographer Don Wood, appeared on a post card produced by Audio-Visual Designs of Earlton, New York. No. 421 was originally No. 4434, but received the low number during the B&O's late steam renumbering to clear the way for new diesels. She went to the torch later the same year.