After Lockheed had introduced its 10-passenger Model 10 Electra, the company decided to develop a smaller version which would be better suited as a "feeder airliner" or a corporate executive transport.

It would carry only six passengers and two pilots but would use the same 450 hp (340 kW) Pratt & Whitney R-985 Wasp Junior SB radial engines as the main Electra version, the 10A.

[2] As it turned out, the other two competition entries, the Beechcraft Model 18 and the Barkley-Grow T8P-1, weren't ready in time for the deadline, so Lockheed won by default.

[3][6] One notable airline user was the newly renamed Continental Air Lines, which had a fleet of three Lockheed 12s that ran on its route between Denver, Colorado, and El Paso, Texas, in the late 1930s.

[6] Sidney Cotton modified these aircraft for aerial photography and in civilian guise, overflew and surreptitiously photographed many German and Italian military installations during the months preceding World War II.

[16] The main military user of the Lockheed 12 was the Royal Netherlands East Indies Army Air Force, which bought 36.

The U.S. National Advisory Committee for Aeronautics (NACA) bought two, adding a center vertical fin to each of them to test stability improvements.

One of the NACA Lockheed 12s was used to test "hot-wing" deicing technology, in which hot exhaust air from the engines was ducted through the wing's leading edge to prevent ice accumulation.

[19] These had their normal landing gear replaced by a non-retracting version with a large nosewheel and with the main wheels shifted further back on the engine nacelles.

This 12A had extra fuel tanks in the cabin, allowing it to save time by making the entire 2,043 mi (3,288 km) trip non-stop.

[18] Another Lockheed 12A, owned by Republic Oil Company and named The Texan, was modified by aviator Jimmie Mattern for a round-the-world flight attempt.

[18] The aircraft was denied a U.S. permit for the flight following the Earhart incident, but was then pressed into action in September 1937 in a long range search effort for Sigizmund Levanevsky, who crashed somewhere between the North pole and Barrow, Alaska.

With the arrival of World War II, Lockheed concentrated its production efforts on more advanced military aircraft, such as the Hudson bomber and the P-38 Lightning twin-engined fighter.