Grafton's population reached its peak at approximately 10,000 in the 1850s with employment opportunities coming from the local stone quarries, boat building and commercial fishing. At one point, there were five quarries in or around Grafton that employed nearly 2,000 men. The local limestone was used to build the Eads Bridge in St. Louis, government buildings in Rock Island, and the Jersey County Courthouse in Jerseyville. The Shafer's Wharf Historic District was one of the largest commercial fishing centers along the Mississippi River in the late 19th century. The Old Boatworks, located south of Main Street, once housed a paint house and a machine shop where paddle wheelers and later PT boats were built. Today, the Old Boatworks building hosts many antique and craft stalls and is open on the fourth weekend of each month from May through October.