Located in central Montgomery County, District 3 includes Gaithersburg, Rockville, Washington Grove, Leisure World, and parts of Aspen Hill, Derwood, North Potomac and Potomac.

District 3 is home to the National Institute of Standards and Technology, Rock Creek Regional Park, part of Seneca Creek State Park, and the Shady Grove Life Sciences Center (including Shady Grove Adventist Hospital).

Bisected by I-270 and Route 355, District 3 is served by several MARC commuter rail and Metrorail stations, including the Shady Grove Metro station.