B&O 2-8-8-4 No. 7604 poses for an unknown photographer at an equally unknown location and date. With a grate area of 117½ square feet, these EM-1s had 5298 square feet of evaporative heating surface and 2118 square feet of superheater surface, and developed 115,000 pounds of tractive effort. (Other details are given on the previous page for No. 7601.) This wheel arrangement was first used on the Northern Pacific; hence the name "Yellowstone" came to be applied to the type. At 628,000 pounds the B&O's version were the smallest 2-8-8-4s built, but they were quite successful. Videos show as many as three of them at a time handling ore trains in their final assignment. No. 7604 became No. 654 in 1957 but was dropped from the roster later that year.