William Penn understood the vital role mills would play in his colony. Along with Penn on the ship Welcome was Caleb Pusey, the man who would manage William Penn's mills. Pusey had on board the framework for a mill. When he arrived at Upland, he served as manager of Chester Mills, the official proprietary saw and grist mills which were the first established in Penn's colony. William Penn attended the laying of the cornerstone and was known to visit Caleb's home, which still exists today.

Gristmills played a vital role in the economic and social development of communities in Pennsylvania and throughout America. As economic specialization increased, the miller provided a technological advancement through the use of natural power that eased the burden individual farmers turning grain into flour. The early settlers created roads to get to the mill and many times other services grew up around the mill complex creating communities.

Wheat became Pennsylvania's principal crop and flour its most important export. Ships took wheat, flour, and "biscuit" (also known as "hard bread" or "ship's bread") to Europe, the Caribbean islands, and Africa.
In 1760 there were well over 150 flourmills in Philadelphia, Bucks, and Chester counties alone. In 1765, Pennsylvania exported 367,222 bushels of wheat and 18,714 tons of flour and biscuit–approximately 85 percent of the colony's exports
During the American Revolution, food was as critical as bullets in keeping an army on the move. George Washington issued orders for his troops to save ammunition and also order gristmills made inoperable by removing the millstones. Mills in proximity to British troops could provide flour for the Redcoats easing the shipment of foodstuffs.

The lesson will look at the making of bread, the mechanics of a water-powered gristmill, the culture of the revolutionary war era, and analyze why gristmills became a focus of armies.