The Grist Mill

The Rock Run Gristmill, one of the oldest mills still standing in Harford County, Maryland, was built in 1794 by John Stump III, a prominent businessman and landowner, on a tract of land once known as the “Land of Promise.” Stump operated several mills throughout Harford, Cecil, and Baltimore Counties.

 

After his death in 1816, the property passed to his daughter Ann and her husband, Dr. John Archer Jr., keeping it in the Archer family until 1904. The mill then changed hands several times until it ceased operations in 1954. The mill was a center of community life. Local farmers brought their grain to be ground, often paying not in money, but by giving the miller a share of the product, known as the “pottle.” Between 1827 and 1856, the mill’s second floor also housed the local post office, making it a hub of both economic and social activity.

 

Originally constructed as a four-story merchant mill, Rock Run ground wheat into flour for both local use and export—especially to the Caribbean. In 1840, the opening of the Susquehanna and Tidewater Canals alongside the mill made it easier to receive wheat and export barrels of flour, further boosting the mill’s commercial reach. Much of the milling process was automated in the early 1800s, requiring only a small crew to operate.

 

Around 1900, the mill underwent major renovations. The traditional millstones used for grinding wheat were replaced with steel rollers, though the old stones continued to be used for grinding corn. That same year, a modern Fitz Waterwheel—an 84-bucket, 12-ton cast iron wheel—was installed. The wheel, powered by falling water, drives a system of gears and pulleys that rotate the French-made millstones inside.

 

The mill ceased grinding wheat in the 1930s, but corn continued to be milled until 1954. In 1960, the Maryland Department of Forest and Parks purchased the site and restored parts of the mill in 1965 for public demonstration. Today, the fully restored Rock Run Gristmill and its replica waterwheel stand in Susquehanna State Park, offering visitors a glimpse into Maryland’s early industrial and agricultural history.