Simplicity Manufacturing began producing lawn equipment in 1937. Simplicity produced lawn tractors for Allis-Chalmers, and the company was purchased by Allis in 1965. In 1983, Simplicity was sold by Allis to management. In 2004, Briggs & Stratton purchased Simplicity.
Simplicity - official site
SimpleTractors.com - information on Simplicity tractors
Michaels Tractors - web forum and information about Simplicity and Allis tractors