Menallen Township was formed in December of 1783. The name is Irish origins and is spelled in all possible ways in the old records, but present spelling is what was finally settled on. It is believed that settle from Adams County in Central Pennsylvania brought the name Manellen with them. The Township was one of the original nine townships established when Fayette County was formed from Wastemoreland County. In 1797, Menallen was split and its western end became Redstone Township. The first settler in Menallen Township was probably William Brown was came here in 1765. The First Church was established in 1784 or before Sandy Hill near Jennings Run on New Salem Road. The first known township supervisor was Joseph Mendenhall who settled here from Philadelphia soon after the Revolutionary War. Mendenhall was a founder of Sandy Hill Quaker Church and a Captain in the Revolution. The first was established on the National Road at Searights where the remains still exist today. President James Polk once spent a night at the tavern when carriage broke down nearby.