Grantsville, MarylandTownThe Casselman River in Casselman River Bridge State Park near Grantsville, Maryland.Location of Grantsville, MarylandCoordinates: 39°41′49″N 79°9′21″WCountryUnited StatesStateMarylandCountyGarrettIncorporated1864[1]Area[2] • Total0.98 sq mi (2.54 km2) • Land0.98 sq mi (2.54 km2) • Water0 sq mi (0 km2)Elevation2,303 ft (702 m)Population (2010)[3] • Total766 • Estimate (2016)[4]764 • Density780/sq mi (300/km2)Time zoneEastern (EST) (UTC-5) • Summer (DST)EDT (UTC-4)ZIP code21536Area code(s)301FIPS code24-34525GNIS feature ID0584690