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is a census-designated place and an unincorporated area in Montgomery County, Maryland, United States.
As an unincorporated area, Darnestown's boundaries are not officially defined. Darnestown is, however, recognized by the United States Census Bureau as a Census-designated Place, and by the United States Geological Survey as a populated place located at (39.101429, -77.281236).
According to the United States Census Bureau, the place has a total area of 17.7 square miles (45.8 km²), of which, 16.6 square miles (42.9 km²) of it is land and 1.1 square miles (2.9 km²) of it (6.27%) is water.