The influence of the Welsh, some of whom were forced by heavy taxation to sell their land, waned in the latter half of the 18th century.

The new township was named 'Radnor' after the county in Wales called Radnorshire. Radnor Township grew around the meeting house and remained the center of population of the township for 200 years. In 1717, the Welsh Friends built a meeting house on a trail made by the Susquehannock Indians in Radnor Township. William Penn, an English Quaker, laid out the township in an elongated rectangle located parallel to the Schuylkill River, and the borders of the township have remained unchanged since its founding in 1682. The parties agreed on a tract covering 40,000 acres (160 km 2), to be constituted as a separate county whose people and government could conduct their affairs in Welsh. In about 1681, a group of Welsh Quakers met with William Penn to secure a grant of land in which they could conduct their affairs in their own language. The original settlers were Welsh-speaking Quakers, led by John Roberts, in an attempt to establish an barony of Wales in Pennsylvania. Radnor Township was founded as a part of the Welsh tract. Radnor Township is one of the oldest municipalities in Pennsylvania. Radnor Township is the largest municipality in Delaware County by land area and the fourth-largest by population, following Upper Darby Township, Haverford Township, and Chester.

As of the 2019 United States census estimate, the township population is 31,875. Radnor Township, often called simply Radnor, is a first class township with home rule status in Delaware County, Pennsylvania, United States.

Radnor township map