The boundaries of the Silver Spring CDP (in dark orange) as of 2010
As an unincorporated area, Silver Spring's boundaries are not officially defined. As of the 2010 Census the
United States Census Bureau defines Silver Spring as a
census-designated place with a total area of 7.92 square miles (20.5 km2), all land; however, it does contain numerous creeks and small lakes. This definition is a 15% reduction from the 9.4 sq. mi. used in previous years. The
United States Geological Survey locates the center of Silver Spring at 38°59′26″N 77°1′35″W / 38.99056°N 77.02639°W, notably some distance from the Census Bureau's datum. By another definition, Silver Spring is located at 39°0′15″N 77°1′8″W / 39°0′15″N 77°1′8″W / 39.00417; -77.01889 (39.004242, -77.019004).
 The definitions used by the Silver Spring Urban Planning District, the
United States Postal Service, the Greater Silver Spring
Chamber of Commerce, etc., are all different, each defining it for its own purposes.
Residents of a large swath of South-Eastern Montgomery County have Silver Spring mailing addresses. This area extends roughly from the
Prince George's County, Maryland and
Howard County, Maryland lines to the west, north and east, and Rock Creek Park and Players Mill Road to the west and north-west. This postal code even includes nearby towns such as Four Corners, Wheaton, Glenmont, Forest Glen, Aspen Hill, Hillandale, White Oak, Colesville, Colesville Park, Cloverly, Calverton, Briggs Chaney, Greencastle, Northwood Park, Sunset Terrace, Fairland, and Kemp Mill. Surprisingly, even a tiny portion of the Langley Park and Adelphi neighborhoods have Silver Spring Zip Codes, though they are in Prince George's County. These boundaries make Silver Spring larger in area than any
Maryland except for
Baltimore. Some notable landmarks are the world headquarters of
Discovery Communications, the
AFI Silver Theatre, the
NOAA headquarters, the world headquarters of the
Seventh-day Adventist Church, the headquarters of the
US Food and Drug Administration,
 and the national headquarters of the
Ahmadiyya Muslim Community.
Downtown Silver Spring in February 2005, as seen from downtown
Parks and recreation
Acorn Park, site of the "silver spring"
Rock Creek Park passes along the west side of Silver Spring, and offers hiking trails, picnic grounds, and bicycling on weekends, when its main road, Beach Drive, is mostly closed to motor vehicles.
Sligo Creek Park follows
Sligo Creek through Silver Spring; it offers hiking trails, tennis courts, playgrounds and bicycling. The latter is facilitated on weekends, when parts of Sligo Creek Parkway are closed to automobiles. The bike trails are winding and slower than most in the region. Recently, rocks have been spread along either side of the road, providing a hazardous bike ride, or skating leisure.
Acorn Park in the downtown area of Silver Spring is believed to be the site of the
eponymous "silver spring".
The 14.5-acre (59,000 m2) Jesup Blair Park was recently renovated and features a soccer field, tennis courts, basketball courts, and picnic area.
Brookside Gardens is a 50-acre (20 ha) park within
Wheaton Regional Park, in "greater" Silver Spring. It is located on the original site of Stadler Nursery (now in
Northwest Branch Park is a 700-acre (280 ha) park surrounding the
Northwest Branch of the
 The park includes hiking, equestrian, and cycling trails on the Northwest Branch and Rachel Carson Greenway Trails. This park is part of Silver Spring and extends farther within Montgomery County. Note that the Rachel Carson Greenway Trail is named after
Rachel Carson, author of
Silent Spring and former resident of Silver Spring.