In the early years after its founding, numerous Scotch-Irish Americans came to the area to farm its rich land.

[7] According to the United States Census Bureau, the township has a total area of 30.76 square miles (79.7 km2), all 0 land.

Penn Township is also part of the Turtle Creek (Monongahela River tributary) watershed.

Penn Township also has a tax collector elected to serve a four-year term.

[9] The district operates eight schools, six of which are in Penn Township: The Murrysville branch of the Westmoreland County Community College is located along Mellon Road.