When the Rock Island introduced its lightweight Rocket streamliners in 1937 they were powered by these 1200-horsepower TA units built by Electro-Motive Corporation. This view provided by Gary Thompson shows unit 601 at Des Moines, Iowa in 1953 when it was in service on the Corn Belt Rocket. The locomotive has been modified from its original appearance by installation of the oscillating headlight, replacement of the retractable front coupler with a standard one, and removal of side skirting over the trucks. The TA model was notable for utilizing the General Steel Castings swing-bolster double-equalized truck (sometimes incorrectly referred to as the "AAR Type B"), whereas later four-axle units produced by Electro-Motive used some variation of the GP or "Blomberg" truck. No. 601 was retired in 1958 and scrapped in 1960.