He formed the C. W. Kelsey Manufacturing Company and produced the three-wheel Motorette car from 1910 to 1912. Later, he manufactured the "Kelsey Motor Company Perfected Friction Drive" car (1920-24). In 1924 Kelsey quit the automobile industry. The Kelsey Motorette was introduced in 1910 in the USA. The vehicle was designed and manufactured by C.W. Kelsey and was produced in limited numbers; about 210 were produced. Power was supplied by a 2-stroke 2-cylinder engine that was initially air-cooled in the first models. A switch was made to water cooled engines by 1911. 

The engine drove the single rear wheel and steering was controlled by a tiller device. The first models produced tended to roll on cornering and anti-sway bars were developed to counteract this. Several hundred vehicles were built and shipped throughout the USA as well as Denmark, Canada, Mexico and Japan. In addition to the standard version, a delivery van was also created as was a rickshaw model that was exported to Japan.

Cadwallader Washburn "Carl" Kelsey built his first 4 wheel car in1897. While still in college he and a classmate, I. Sheldon Tilney, designed a single cylinder, 5 hp vehicle with 2 wheels in the front and 1 in the rear. They called it the "Autotri". Sons of wealthy Philadelphians, the boys’ fathers intervened in the work, sending their sons back to school work because the automobile was "an instrument of the devil". By 1901 Kelsey was consorting with the devil again when he built a 2 cylinder, 4 wheeled auto. In 1902 he began to sell Maxwell autos and he worked for Maxwell Motor Co. as its Sales Manager from 1905 - 1909. Sensing disaster coming at Maxwell, he left to begin making cars of his own.

1910 Kelsey Motorette