 CTA 5001 was one of four three car articulated trainsets delivered from Pullman Company (5003 and 5004 by St. Louis Car Company) in 1948 to test PCC components for rapid transit cars.Because of their high speed and large capacity they were used on the Skokie Swift exclusively between 1964 and 1985, where they were renumbered 51-54.CTA 6101-6102 were built by St Louis in 1950.