CTA's largest series of cars are 2601-3200, built by Budd in 1981-1987. Cars are assigned to the Red Line, the Blue Line, and a few to the Purple Line. Location is the Belmont stop on the Red Line in 1996, prior to rebuilding by by Alstom in Hornell, NY.
All of the 2600 series cars have been rebuilt by Alstom in Hornell, NY. Rebuilt cars appeared with a simpler paint scheme. Location is the Belmont stop on the Red Line.
CTA's next group of cars cars was the series 3201-3457, built by Morrison-Knudsen in 1991-1994. These were the first cars originally constructed for one person operation with full width cabs, and are used on the Brown Line and the Orange Line. Location is the Randolph/Wabash stop on the Loop elevated line.
Cars 3441-3456 were delivered with pantographs for the "Skokie Swift" Yellow Line, half of which used overhead catenary until 2004. Location is the Skokie station on Dempster St.
CTA's newest cars are the series 5001-5406, built by Bombardier in 2009-2013. These cars first entered regular service on April 19, 2010. On that date, car 5003 leads a southbound Red Line train at the Cermak/Chinatown stop. The cars look similar to the 3200 series cars, but have electronic signs, and mostly sideways facing seats.