Alcohol Treatment Center in Harding, NJ.

After the retreat of the Wisconsin Glacier, a mighty glacial lake called Glacial Lake Passaic formed in this area that, about 15,000 to 11,000 years ago, extended for 30 miles (48 km) in length and was 10 miles (16 km) wide. The lake finally drained when a blockage of the Passaic River reopened. The Great Swamp is the remnant of the lake bottom and portions of the swamp lay in what now is the township. Once the lake drained, higher areas became a wooded area that was used for hunting, fishing, and farming by Native Americans. At the time of colonization by the Dutch it belonged to the Lenape tribes, but British colonists did their best to displace them westward.

Much of what now is known as Harding was an agricultural community with roots stretching as far back as the early 18th century. Bypassed by colonial turnpikes, revolution era canals, and railroads laid in the Victorian era, the area remained a rural backwater. For almost two centuries of European occupation, its open and rolling landscapes reflected its agricultural use, as land had been cleared for cattle pastures, orchards, and fields of grain. The Great Swamp, the wooded slopes of the Watchung Mountains, and those near Jockey Hollow also were used by local farmers for wood supply. The communities of Green Village, Logansville, New Vernon, and Pleasantville were the village centers in this agricultural community.

Wealthy urban residents from Manhattan and Newark bought farmland, enlarged old farmhouses, and landscaped the grounds. The movement to establish Harding Township was driven by local property owners who wanted to maintain a bucolic community without suburban development.