Orange Grove Flour Mill, Ruins of a flour mill in Patapsco Valley State Park, Maryland

The Orange Grove Flour Mill was a six-story structure in Patapsco Valley State Park, standing between CSX Railroad tracks and the Patapsco River. The mill operated from 1856 to 1905, processing grain into flour for distribution across the region.

The mill was established in 1856 and became one of the region's major industrial operations under the C.A. Gambrill Manufacturing Company. Production ceased in 1905 as new technologies and changing market demands shifted the flour industry elsewhere.

The mill was central to life in this river valley, with workers crossing a swinging bridge daily from their homes in Howard County. The brand name Patapsco Superlative Patent flour became known throughout the region, reflecting the pride locals took in their workplace.

Visitors can reach the ruins by walking about 1.3 miles from the Lost Lake entrance or about 1 mile from Ilchester Road along the Grist Mill Trail. The path follows the river, so comfortable walking shoes are recommended and the area can be muddy in wet weather.

The mill's name comes from osage-orange trees that once grew near the site, not from citrus groves which never existed in this region. These trees are native to the American South and were planted locally for their fruit and hardy wood.