Passaic County is shaped like a bent hourglass with the area above the neck running generally north and south and the portion below, east to west. The upper half of Passaic County is characterized by large lakes and watershed areas with low-density development. The lower half of Passaic County contains more than 85% of the population in a third of the area. Passaic County has 16 municipalities. West Milford Township, at the northern tip of Passaic County, is the largest in size with 78.30 square miles of land. The Borough of Prospect Park is the smallest with .45 square miles of land.
The highest point in Passaic County is Bearfort Mountain in West Milford with an elevation of 1,484 feet. Passaic County’s lowest spots are tidal lands along the Passaic River in Passaic and Clifton. Passaic County has over 40 lakes and ponds with areas in excess of 20 acres, as well as nine reservoirs.