Allamuchy is located in Warren County along the Pequest River. The Musconetcong River forms the Township's southeastern border.

Most of Allamuchy's 21 square miles are still forests and farms. The only substantial development is the Panther Valley community at the juncture of Interstate 80 and Route 517, a 1,200-home development of single-family homes, condominiums, and townhouses.

Township officials are trying to limit the further growth of development in the township. Open space acquisition is a major part of this strategy. The Township and its very active Environmental Commission are aggressively pursuing state Green Acres money and have put together a detailed open space plan for the Township.