Horton, an 1895 electrical engineering graduate of the University of Michigan, was credited with the invention of the safety switch, which encased high voltage switches and started the company's main line of business of circuit breakers and encased control panels.

The combination of an easily remembered monogram logo and their great popularity resulted in customers referring to their products as "Square D".

directed public attention to the lethal hazard of exposed electrical switches in factories.

By 1929, Square D merged with a Milwaukee-based industrial controller company and began producing Westinghouse-licensed circuit breakers.

Today the company produces several lines of circuit breakers for domestic, commercial, and industrial applications.