In 1934, the original Lawn-Boy lawn mower was manufactured by the Evinrude Company, becoming the first one-handed reel power mower introduced to the American public. Evinrude purchased Johnson Motor Wheel Company from a New York stock brokerage firm a year later, and in 1936 they merged with the Outboard Marine and Manufacturing Company (OMC), continuing production of Lawn-Boy mowers until 1939, when it was temporarily put on hold to manufacture outboard motors for World War II. In 1946 and after the war, Joel G. (Jack) Doyle built the first rotary lawnmower for the Rotary Power Mower Company of Kansas City, Missouri. Doyle accumulated orders for these mowers from Sears Roebuck, Gimbles, Spiegel, and other businesses. OMC then bought RPM in 1952, and changed the brand of the rotary lawn mower to the Lawn-Boy name.
In the 1950s, RPM facilities were converted to production line manufacturing to meet the high number of orders from bigger retailers such as Sears Roebuck and Spiegel. Also, newer, quieter engines were introduced to reduce sound.
The next couple of decades included a long period of research and development as the company continued to expand, including overseas. Riding mowers, tillers, and snow blowers were introduced, as well as a new 2-stroke engine in 1970 that produced more power, with less weight and fewer parts. During this time the D-400 engine became popular.
In 1988, Lawn-Boy acquired Gilson Brothers Co., a Wisconsin-based manufacturer of outdoor power equipment and recreational equipment.
In 1989, Lawn-Boy was acquired by The Toro Company, and eventually consolidated to the Toro headquarters in Bloomington, Minnesota. Since the acquisition by Toro, Lawn-Boy has introduced new series of lawn mowers, including a new lineup of walk-behind mowers and an entirely new category of Zero Radius Turning mowers.