Hart Parr was a very early American builder of gas tractors with the Hart Parr 30-60 being one of the more successful “Prairie” style tractors. However by 1919 the Prairie style tractors were obsolete being far too big and clumsy for the average farmer of the time.  The need was for a smaller more nimble tractors. Hart Parr’s first attempt to meet the needs of farmers at the time, the “Little Devil”, was a complete failure and the tractors were recalled. However, the right direction was taken in 1918 with the “New Hart Parr” 12-25 model, which formed the basis for all subsequent Hart-Parr tractors. The “New Hart Parr” was a tractor equipped with a two-cylinder, slow speed, water-cooled engine with force feed lubrication and open gears used to drive the rear wheels. The design after testing in Nebraska was re-rated at 15-30. The 15-30 design was replaced in 1924 by the 16-30 design which was upgraded in 1926 to become the 18-36. These designs could either burn gasoline or kerosene as fuel.

Hart Parr 15-30s are sometimes referred to as 15-30 Type As, 15-30 Type Bs or 15-30 Type Cs. A number of changes were made over production to the water pump, valve levers and push rods and these changes are differentiated by the model designations.