It originally extended as far south as Versailles (modern-day North Versailles Township), east to the county line, west to Pitt Township, and north to the Allegheny River.

Plum has shrunk greatly over the years in area, but still remains among the larger municipalities in Allegheny County.

[5] The 1889 history of Allegheny County, Pennsylvania, describes the township as having "no villages of importance", but listed the first postoffice, Antrim, 1840–1857; New Texas, a hamlet, in the geographic center of the township with "the usual mechanics, local stores, etc.

", post office from 1856; and Logan's Ferry, on the Allegheny River and Allegheny Valley railroad, in the northeastern part of the township, deriving its name from early settler Alexander Logan and family, post office from 1844.

Another explosion on March 5, 2008, which killed one and injured one was also caused by failure of gas pipes.

Boroughs in Pennsylvania (including Plum) are governed by a Mayor-Council system; in which the mayor has only a few powers and the council is the main legislative body.

The Plum Borough School District is governed by a nine-member Board of Directors.

The library houses the history room of the Allegheny Foothills Historical Society (the Historical Society also provides tours of the reconstructed Carpenter Family Log House in Boyce Park).