According to the U.S. Census Bureau, the township has a total area of 14.4 square miles (37 km2), all land.

The Scotch-Irish Presbyterians of Allen Township established a church, in 1731, made of logs.

At the start of the Revolutionary War, John Ralston was the auditor of depreciations, George Palmer was coroner, William McNair and Jacob Horner were justices of the peace.

Neigal Gray and John Ralston attended the provincial conference held in Carpenter's Hall.

Arthur Lattimore, Neigal Gray, and John Hays, Jr. were on the Standing Committee of Correspondence.

Arthur Lattimore was a Justice of the Courts of General Quarter Sessions and of Common Pleas.

The fort is near the present intersection of Route 329 and Airport Road in a farmer's field.

Horner's Cemetery contains the graves of many of the region's earliest inhabitants, including 21 veterans from four U.S. wars.

There is a stone for Robert Brown, a lieutenant colonel in George Washington's Flying Camp, who served in Pennsylvania's State Assembly and then the U.S. Congress after his service in the American Revolutionary War.

George Palmer, Deputy Surveyor-General of Pennsylvania, and Surgeon-General Dr. Matthew McHenry are both buried there.

James Ralston also laid out the town of Bath and Gen. William Lattimore owned the first house there.

PA 248 follows the Bath Pike along a northwest-southeast alignment across the northeastern portion of the township.

PA 512 follows Bath Pike along a north-south alignment across the eastern portion of the township.