The EMD E6 was a 2,000-horsepower (1,500 kW), A1A-A1A, passenger train locomotive manufactured by Electro-Motive Corporation, and its corporate successor, General Motors Electro-Motive Division, of La Grange, Illinois. The cab version, E6A, was manufactured from November 1939 to September 1942; 91 were produced. The booster version, E6B, was manufactured from April 1940 to February 1942; 26 were produced. The 2,000-horsepower (1,500 kW) was achieved by putting two 1,000-horsepower (750 kW), 12-cylinder, model 567 engines in the engine compartment. Each engine drove its own electrical generator to power the traction motors. The E6 was the seventh model in a long line of passenger diesels of similar design known as EMD E-units.

Compared with passenger locomotives made later by EMD, the noses of the E3, E4, E5, and E6 cab units had pronounced slants when viewed from the side. Therefore, these four models have been nicknamed "slant nose" units. Later E models had the "bulldog nose" of the F series.

The original City of New Orleans began in 1947 as part of the Illinois Central Railroad, and was the longest daylight run in the United States. The daylight train under that name ran through 1971, when it was moved to an overnight schedule as the Panama Limited. The present name was brought back in 1981, still on an overnight schedule. The train is the subject of the bittersweet 1971 song "City of New Orleans", written by Steve Goodman