How it started
Square D began in Detroit in December 1902, when Bryson D. Horton and James B. McCarthy set up a small company to make enclosed cartridge fuses. Detroit’s new auto plants needed safer electrical gear, and the company went by a couple of names in its early years, including Detroit Fuse & Manufacturing from 1908.
Sources: Control Engineering: Square D marks 100 years in power, control fields (2002) Encyclopedia.com: Square D (company history) Schneider Electric: Square D Retail Products Catalog, “Our history” page (2016, distributor-hosted PDF)
The square D
In 1909 the company introduced an enclosed safety switch. Its mark, a capital D inside a square, became so well known that in 1917 the company renamed itself after it.
Sources: Encyclopedia.com: Square D (company history) Schneider Electric: Square D Retail Products Catalog, “Our history” page (2016, distributor-hosted PDF)
Into breakers and panels
Square D built its first power distribution panel in 1926. In 1929 it began making circuit breakers under a license from Westinghouse, and it soon launched breakers of its own, including what its catalog calls the first circuit breaker for homes. The catalog dates that to 1930; an encyclopedia history says 1935, so we show both.
Sources: Schneider Electric: Square D Retail Products Catalog, “Our history” page (2016, distributor-hosted PDF) Encyclopedia.com: Square D (company history)
QO and Homeline
In 1955 Square D introduced QO, short for “Qwik-Open,” breakers and load centers. In 1968 it added Visi-Trip, a small window that shows when a QO breaker has tripped. Homeline arrived in 1991. Its catalog also lists ground-fault (1971) and arc-fault (1999) devices along the way.
Sources: Schneider Electric: Square D Retail Products Catalog, “Our history” page (2016, distributor-hosted PDF) Schneider Electric FAQ FA174050: QO Visi-Trip
Who owns it now
In 1991 Groupe Schneider of France, today called Schneider Electric, bought Square D after a takeover fight. By late May 1991 it owned about 98% of the shares. Square D carries on as a Schneider Electric brand.
Sources: The New York Times: Square D Agrees to Takeover (May 13, 1991) The New York Times: Schneider Owns 98% of Square D (May 30, 1991)
This is a history, not an endorsement. IES isn’t affiliated with Square D, and its name and product names are trademarks of their owners. We use plain text, not logos.