[7] Arrowheads found in Munsee encampments throughout the Washington Valley suggest that they hunted wolf, elk, and wild turkey for game.

[8] In the 17th century, Munsee Lenape fishermen made an annual pilgrimage from the Washington Valley to the Minisink Island on the Delaware river, in part to procure shellfish.

Led by Reverend John Brainerd, colonists forcefully relocated 200 people to a land reservation named Brotherton in Burlington County,[10] an industrial town known for gristmills and sawmills.

[17] In the 18th century, Washington Valley became a suburb of the city of Morristown; residents would travel into town for church services and to sell farm products.

A schoolhouse is the only non-residential historic building in Washington Valley, displaying its lack of significant local commerce and industry.

Circa 1960, the Morris County Municipal Utilities Authority purchased land along the Whippany River in an effort to construct a reservoir.

The John Smith House, built in 1812 and located at 124 Washington Valley Road, was added to the NRHP on January 1, 1976.