Settled in the late 17th century, Tredyffrin is bounded by Delaware and Montgomery counties.

It includes on its northern boundary a small part of Valley Forge National Historical Park, where George Washington encamped during the American War of Independence.

Tredyffrin is bordered by Easttown, East Whiteland, Willistown, Charlestown, Upper Merion, Radnor and Schuylkill townships.

On March 13, 1684, William Penn decided to set aside a portion of what was then the Province of Pennsylvania for settlements for Welsh immigrants.

However, there were enough members of this Baptist church that by 1722, a log building was erected in Tredyffrin to serve the congregation.

Tredyffrin-Easttown school district was unusual for the area in being racially integrated during the early part of the century.

During the Cold War, a Nike anti-aircraft missile site was active in the township.

171, Cramond, Cressbrook Farm, Federal Barn, Great Valley Mill, Greenwood Farm, David Havard House, Lafayette's Quarters, Maj. Gen. Lord Stirling Quarters, Mount Zion A.M.E. Church, Strafford Railroad Station, Valley Forge National Historical Park, Joseph Walker House, Van Leer Cabin, and Wetherby–Hampton–Snyder–Wilson–Erdman Log House are listed on the National Register of Historic Places.

In addition, the Wharton Esherick Museum is listed as a National Historic Landmark; it was built starting in 1926.

U.S. Route 422 begins at US 202 in the northeastern corner of the township and follows the County Line Expressway northwestward.

U.S. Route 30 follows Lancaster Avenue along an east-west alignment through the southern section of the township.

[9] As of the 2000 United States census, there were 29,062 people, 12,223 households, and 7,834 families residing in the township.

Mitt Romney vastly improved upon McCain's performance, but still fell short as Obama carried the township with 52% of the vote in the 2012 presidential election.

The rocks of Tredyffrin were laid down in the upper Paleozoic, meaning that they are primarily metamorphic.

"[17] In 1990 a new children's library was created on the lower level of the building in previously unfinished space.

[20] As the community continued to grow and change, plans were finalized in 2004 to renovate and expand Tredyffrin Library.

According to the publication, the shared concepts were "unusual sensitivity in using natural light to best advantage while warding off the sun," a "quickly apparent organization of functions," and being "responsive to the varying situations in which it is built.