Once the heart of a lively community called Milltown, the Cooper Gristmill is one of the remaining waterpowered mills in New Jersey. It still runs today using historic technology and waterpower from the nearby Black River. At the visitor center, located in the old Cooper house, exhibits focus on the social, agricultural and technological aspects of the residents' life in the late 19th and early 20th centuries.

In 1760, Isaiah Younglove was traveling on the Washington Turnpike, as the road crossed the Black River he realized this area was an ideal site for water power. He recognized the need of local people for a gristmill to grind flour for home use and coarser meal for animal feed. He built a gristmill and sawmill at this location where the river begins to flow rapidly downhill for several miles In fact, the river powered 5 sawmills and 3 gristmills at one period. The walls of one of those old sawmills can be seen behind Cooper mill.

Isaiah’s mills changed owners several times. In 1825 it was for sale to settle the estate of Elias Howell. Nathan Cooper was a business man who saw the opportunity to expand his business ventures into the milling area. That year he purchased the gristmill, saw mill, mill dam, mill wheels, including all the machinery, and 4 ½ acres of land for $750. Nathan Cooper tore down the original building and replaced it with the stone structure that you see today. His new gristmill was capable of twice the production of merchant grade fine white flour. He used the processed developed by Oliver Evans a late 1700's inventor. .Evan's ideas revolutionized the flour milling industry by designing and building a gristmill that, once started by water power, could run by itself. Cooper Mill still operates using this intricate system. The entire 4 story building functions as one big machine to grind grains like wheat and corn into flour.

The community of Milltown flourished due to its proximity to the river, rich iron ore deposits, fertile farmland, abundant timber and connecting roadways. It expanded to include a blacksmith shop, general store, school, several homes and a distillery among other buildings. Cooper mill played a vital role in the area's development during the Industrial Revolution.

In 1870, Nathan' son Abram took over the operation of the mill. Soon after, milling and iron mining became more important out West, many workers moved away. By 1914 it had completely ceased grinding.

In 1963 the Morris County Park Commission (MCPC) became stewards of this 14 acre property.MCPC contracted Richard and John Federowicz to restore the mill. Operating one run of millstones powered by a Fitz steel overshot waterwheel, The Cooper Gristmill opened in October of 1978. Visitors could see the 16 foot waterwheel turn the millstones on the main floor and go down the stairs to observe the meal/flour coming down the chute into the meal bin. Over the years, many other restoration projects have opened up new sections of the building to the public.This includes: the miller’s office and the 2nd and 3rd floors with all the machinery for 2 runs of millstones. On the upper floors visitors can see the cleaners and bolter and bag hoist operating. All the additional machinery is still powered by the Fitz steel overshot waterwheel installed in the 1970’s.