The Farmall B is essentially the same tractor, but with the engine centered for narrow front wheels, and the seat offset instead of the engine, with a wider range of rear wheel adjustment for two-row cultivation. Versions were produced for both gasoline and kerosene fuel. Rear wheels on all models used a geared portal axle to provide sufficient ground clearance, and could be adjusted in width over a range of 40 inches (100 cm) to 68 inches (170 cm).

As with other Farmall letter-series tractors, the design featured an integral frame and unitary construction, allowing entire assemblies to be replaced. The A featured a wide front wheel track with an offset engine, intended to allow for a better view ahead and branded 'Cultivision.' The offset engine benefited front-mounted cultivators, compared with the towed equipment used by competing Ford-Ferguson tractors. The transmission contains five total gears in a sliding gear arrangement: four forward and one reverse, transmitted to a portal axle. The Farmall A is equipped with the F-14's International Harvester C113 4-cylinder inline overhead valve engine, with a 113-cubic-inch (1,850-cubic-centimetre) displacement. The A was rated for one 14-inch (36 cm) plow. Styled by Raymond Loewy, it was one of International Harvester's ' letter series', with 117,522 produced over the 8-year run, replacing the Farmall F-14. The most significant change was the introduction of hydraulics with the Super A. An International Harvester C113 4-cylinder in-line engine was used for early models, increased to an IH C123 with the A-1. Like the smaller Farmall Cub, the Farmall A features a distinctive offset engine, displaced to the left over wide-set front wheels, to allow vision straight ahead.

The A was incrementally updated with new model numbers as the Super A, 100, 130 and 140, but remained essentially the same machine. The tractor was popular for its set of innovative features in a small, affordable implement. The Farmall A is a small one-plow row crop tractor produced by International Harvester under the Farmall brand from 1939 to 1947.

Farmall 140 tractors serial numbers