In the mid-to-late 1940s the T-1 4-4-4-4 duplexes handled the Pennsylvania Railroad's premier passenger trains in non-electrified territory. They were known for their speed, and had the horsepower to pull a 16-car passenger train at a steady 100 miles per hour — outperforming the 5400-horsepower diesels of the day, and making it possible to replace double-headed K-4s Pacifics with a single locomotive. The T-1 class had 80-inch drivers and four 19¾x26-inch cylinders, and sustained 300 p.s.i. of boiler pressure. (Nine locomotives later had their cylinder diameter reduced to 18¾x26.) They had a grate area of 92 square feet, 4209 square feet of evaporative heating surface, and 1430 square feet of superheating surface. The T-1 developed 58,300 pounds of tractive effort. No. 5527, a Baldwin product, poses above at Englewood Station, Chicago, in a photo of indeterminate origin. Although originally built with a more streamlined front end having three side "port­holes" (see the preceding photos of No. 5526), all or most were later modified with access steps from the pilot to the catwalk as shown here. None of the T-1s survive — the last few went to scrap in 1954, according to one source — but they will be remembered as a bold attempt to meet the challenge of the diesel on its own terms.