Thornbury Township lies in the drainage area of the Delaware River, named in honor of Thomas West, governor of the colony of Virginia.

The river and its bay were explored by Henry Hudson in 1609, and over the next several decades the region was variously claimed by the Swedes, the Dutch, and the English.

Once the Dutch were defeated, King Charles II of England made his grant to William Penn in order to found the colony which came to be named Pennsylvania.

The original grant documents were copper-plate prints on parchment; some still survive and show a price of 100 English pounds for 5,000 acres (2,000 ha).

Thornbury was named after the English birthplace of the wife of George Pearce, who in 1685 had been granted title to 490 acres (200 ha) in the township.

The township is the location of "Thornbury" house, home of Revolutionary War figure Persifor Frazer.

After the Battle of Brandywine, his wife Mary stood down a British raiding party in a celebrated incident.

[9] In September 2000, the Delaware Nation of Oklahoma received 11.5 acres of land in Thornbury Township.

[10] The George W. Hill Correctional Facility (Delaware County Prison) is partially located in the township.

Postal Service operates the Cheyney, Glen Mils, and Thornton post offices.

[16] Three elementary schools serve sections of the township: Penn Wood, Sarah Starkweather, and Westtown-Thornbury.

Glen Mills Schools, a residential facility for male juvenile delinquents, is in Thornbury Township.