The first European settler in present-day Upper St. Clair was John Fife, who settled near what is now the intersection of Washington and McLaughlin Run roads in 1762.
St. Clair Township, named after General Arthur St. Clair of Revolutionary War fame who was the 9th President of the United States in Congress Assembled. Under his administration as President, February 2, 1787 to October 29, 1787, the Northwest Ordinance and United States Constitution of 1787 were passed.
St. Clair was one of the original townships of Allegheny County, Pennsylvania at the county’s creation in 1788. In 1836, the St. Clair Township was divided into two separate townships, Upper St. Clair and Lower St. Clair. The residents of Upper St. Clair formed their township to ensure better government service that could be obtained by separating from the more densely populated northern part of the township. Upper St. Clair Township was further subdivided throughout the 19th and 20th centuries as several parts of the original township separated to form new townships and boroughs. In 1973, Upper St. Clair Township adopted a home rule charter that took effect on January 5, 1976, and is no longer governed by the Pennsylvania Township Code.
The Whiskey Rebellion of 1794 had roots in Upper St. Clair.
Formed as a volunteer militia company in 1844 by residents of the township, the “St. Clair Guards” later became Company H of the 62nd Pennsylvania Volunteers.
The community was home to several mines beginning in the late 19th century. Freehold Real Estate Co. built the first major residential development in March 1913 along Washington Road that at the time was conveniently close to streetcar service.
As of today, the community has many fashionable homes and is considered one of the wealthiest suburbs of Pittsburgh.