Hart-Parr Farm tractors by power
Hart-Parr was founded in 1901 by Charles Hart and Charles Parr, both engineering students at the University of Wisconsin. Hart and Parr are two of the early pioneers of gasoline tractor design. Hart-Parr was the first American manufacturer to put gasoline tractors into production in 1903, and can make a claim to being the first in the world (the English Ivel firm also began production that year). In 1929, Hart-Parr merged with Oliver Chilled Plow to form the Oliver company.
Hart-Parr Tractors - information and photos of Hart-Parr tractors
| Model | Power | Years |
| 20 | 22 hp[B] | 1920 - 1924 |
| Little Devil 25-22 | 24 hp[B] | 1914 - 1916 |
| 12-24 | 26 hp[B] | 1924 - 1930 |
| Crop Maker 17-27 | 30 hp[B] | 1916 - 1917 |
| Row Crop 18-27 | 30 hp[B] | 1930 - 1935 |
| 18-28 | 31 hp[B] | 1930 - 1936 |
| 16-30 | 33 hp[B] | 1924 - 1926 |
| 17-30 | 33 hp[B] | 1901 - 1906 |
| 30 | 33 hp[B] | 1919 - 1924 |
| New Hart-Parr | 33 hp[B] | 1918 - 1919 |
| Oil King 23-35 | 38 hp[B] | 1916 - 1919 |
| 18-36 | 40 hp[B] | 1926 - 1930 |
| 20-40 | 44 hp[B] | 1912 - 1914 |
| 40 | 44 hp[B] | 1923 - 1927 |
| Steel King | 44 hp[B] | 1916 |
| 28-44 | 48 hp[B] | 1930 - 1937 |
| 22-45 | 50 hp[B] | 1903 - 1911 |
| 28-50 | 55 hp[B] | 1927 - 1930 |
| Old Reliable 30-60 | 66 hp[B] | 1907 - 1918 |
| 40-80 | 110 hp | 1908 - 1909 |
| 60-100 | 111 hp[B] | 1911 - 1912 |
[B]: Engine power estimated from belt horsepower. See individual tractor data listing for power details.