The 2-10-4 acquired the designation "Texas type" because the Texas & Pacific was the first railroad to use this new "Super-Power" design from Lima Locomotive Works. Lima delivered the first ten, in class I-1, in 1925 and repeat orders soon followed until by the end of the decade the line rostered 70 of these heavy-hauling oil burners. No. 637, shown in this builder's photo from Rand McNally's 1951 edition of World Railways, represents the I-1b class delivered in 1928. They had 63-inch drivers, 29x32-inch cylinders, and 255 p.s.i. of boiler pressure. With a locomotive weight of 448,000 pounds, they exerted a tractive effort of 84,600 pounds with a booster adding 13,300 pounds for starting heavy trains. Their evaporative heating surface totaled 5,113 square feet, plus 2,100 square feet of superheating surface, and their large 100-square-foot grate area further contributed to their steaming capacity. Their flanged stack was a typical feature of T&P steam locomotives. Late photos reveal that some examples of the Texas & Pacific 2-10-4s were modernized with disc drivers and a redesigned trailing truck.

This relatively low-drivered design was closely duplicated in the 35 coal-burning 2-10-4s that Lima, and Baldwin Locomotive Works, delivered to the Chicago Great Western in 1930-31. Subsequent development of the Texas type, however, usually featured a larger driver diameter to take advantage of the speed potential of its steam-producing capability; the culmination was reached in the 74-inch drivers of the Santa Fe's 5001 and 5011 classes, the latter delivered in 1943. As for the T&P's 2-10-4s, No. 610 of class I-1a was preserved and restored to service in 1975 on the American Freedom Train. It was then modified to resemble a Southern Railway engine and took part in that railroad's steam excursion program; it is preserved at the Texas State Railroad.