[2] The town is home to the Helen Woodruff Smith Bird Sanctuary and Annie Duncan State Forest.

Plainfield also includes the village of Meriden, home to Kimball Union Academy, a private preparatory school.

It was one of the towns incorporated by colonial governor Benning Wentworth in 1761, at the beginning of the reign of King George III.

A part of Plainfield known as "Meriden Parish", named for the farm of Massachusetts Governor Jonathan Belcher, became the site of Kimball Union Academy, built in 1813.

[5] Parrish purchased land close to his parents' estate in 1898, at the age of 28, and relocated after leaving Philadelphia.

[citation needed] In 1910, Ernest Harold Baynes founded the Meriden Bird Club, the first institution of its type in the nation.

Grantham Mountain, a peak along the ridge, is the highest point in Plainfield at 2,660 feet (810 m) above sea level.