Franklin Township was founded in 1850, one year after the formation of Lawrence County from parts of Beaver and Mercer. The new county line had bisected Perry Township, leaving the smaller portion in Beaver County. From this part of Perry and that part of Marion Iying north of Connoquenessing Creek, the new Franklin Township was formed.
A singular early industry was the Bassenheim Iron Furnace built by Dr. Detmar Basse (founder of Zelienople) in 1814. Possessing a capacity of five tons of pigs and castings per week, the furnace was sold to Daniel Beltzhoover in 1818 and continued to operate until 1824. The ruins of the furnace may still be seen. Another early industry was the mill built by James and John Hazen on Connoquenessing Creek about 1820. Other early settlers, beside the Hazens, were the Severn, Nye, and Fisher families.
Early churches in the township include the Camp Run United Presbyterian, organized in 1872, and St. Mark's Evangelical Lutheran Church at Lillyville, dating to 1875.
While Weyand and Reed's 1876 Centennial Directory of Beaver County lists more Franklin Township taxables as farmers, Warner's 1888 history stated that "very fine Darlington coal is mined in this district."
Also in 1876, the Baltimore and Ohio Railroad built along the Connoquenessing Creek, affording better transportation to the area. A post office was established at Lillie or Lillyville (which had earlier been known as Stefflerville) in 1893.
Other early villages in the township were Frisco (named for the gold rush city of 1849), Celia, and Fombell. Fombell Post Office recently celebrated its 100th Anniversary with a simulated "wild west holdup." The post office for North Sewickley village was located north of the Connoquenessing in Franklin Township. Frisco, at the junction of Routes 65 and 288, has become the administrative center of the community, with township police and fire headquarters located there.
About the turn of the century, the Harmony Line connected Zelienople, Ellwood City, New Castle, and Beaver Falls by streetcar tracks, passing through Franklin Township.
The township has remained largely agricultural since then, however, with over 6,000 of its 11,500 acres still being farmed today, and an additional 3,500 acres devoted to woodlands and other non-urban uses.
Recent growth in Franklin reflects its suburban position between Ellwood City and Zelienople. In 1970, the Beaver County Court disapproved the attempt by Zelienople to annex the airfield in Franklin Township adjacent to the Butler County Borough. Camp Fombelina, a Girl Scout Camp, is located in the township. Franklin Township, North Sewickley and Marion Townships form the Riverside School District.