About 1736, Peter Willocks built a sawmill along the Blue Brook to produce lumber needed by farmers settling this frontier area, and the operation cleared the forest from hundreds of acres. In 1845, David Felt bought 760 acres of land and built a printing factory along the brook, then created an entire town on the bluff above it to support the mill operation, and by 1850, 175 people were living in Feltville. After Felt retired in 1860, other business ventures were tried but failed, and the town became deserted for a short time. In 1882, Warren Ackerman bought the property and converted the former mill town into a summer resort called Glenside Park. When the popularity of mountain resorts was displaced by the advent of the Jersey Shore, Glenside Park closed in 1916. Soon after the Union County Park System was formed in 1921, the area was incorporated into the Watchung Reservation, one of America's first county parks.