Other organizations, such as the U.S. Geological Survey, U.S. Postal Service, Silver Spring Urban Planning District, and Greater Silver Spring Chamber of Commerce, each use their own slightly different definitions. The Postal Service in particular assigns Silver Spring mailing addresses to a large swath of eastern Montgomery County sometimes called "Greater Silver Spring," including Four Corners, Woodmoor, Wheaton, Glenmont, Forest Glen, Forest Glen Park, Aspen Hill, Hillandale, White Oak, Colesville, Colesville Park, Cloverly, Calverton, Briggs Chaney, Greencastle, Northwood Park, Ashton, Sandy Spring, Sunset Terrace, Fairland, Lyttonsville, Kemp Mill, a portion of Langley Park, and a portion of Adelphi. The area that has a Silver Spring mailing address is larger in area than any city in Maryland except Baltimore.