Allis Chalmers contracted with Simplicity to produce lawn and garden tractors in 1961. Allis purchased Simplicity soon afterwards, and built an extensive line of lawn tractors. In 1983, Allis sold Simplicity and Allis was purchased by Deutz, ending the Allis-Chalmers brand name for 25 years. In 2008, Briggs & Stratton (the new owner of Simplicity) resurrected the Allis-Chalmers brand name on the new AC130 line of lawn tractors.
SimpleTractors.com - extensive information on Allis lawn tractors