Marion Township, nestled between the Connoquenessing and Brush Creek Valleys, is largely farmland. Two well known recreational camps are located in the township: YMCA's Camp Kon-O-Kwee and YWCA's Camp Carondawanna, established in the 1920's, attract youth from Butler and Allegheny Counties as well as Beaver County. Brush Creek Park, shared with neighboring North Sewickley Township, continues the traditional role of recreation in the community.
Named for the "Swamp Fox" of the Revolution, General Francis Marion, the township was formed in 1845 when overlarge North Sewickley was split into four townships. Marion was reduced in size by nearly half only five years later when Franklin Township was formed. No village has ever developed in the township, but a post office, Barrisville, served the area until 1901.
The Baltimore and Ohio Railroad crosses the northeast corner of the township. North of the railroad, the land within a large loop of the Connoquenessing Creek has been ruined by strip mining. The Pittsburgh, Harmony, Butler, and New Castle interurban line followed the creek from Zelienople to Ellwood City, providing first class commuter service from 1908 to 1937, but no traces of the trolley remain, except for a private right-of-way above the Connoquenessing between the Hazen Bridge and Dambach's evergreen nursery.
Bernhard Mueller's 1814 stone house, "Ben Venue," was a prominent landmark along Route 68 in the eastern part of the township. Mt. Pleasant Cemetery, recently restored, contains the graves of several Revolutionary soldiers. Today, Marion remains a rural community, with most services provided by neighboring Zelienople and Cranberry Township. The development of Brush Creek Park and expansion of Cranberry Township provide the greatest challenge to the community in its history.