Silver Spring is a census-designated place (CDP) in southeastern Montgomery County, Maryland, United States, near Washington, D.C. Although officially unincorporated, it is an edge city with a population of 81,015 at the 2020 census, making it the fifth-most-populous place in Maryland after Baltimore, Columbia, Germantown, and Waldorf. Downtown Silver Spring, located next to the northern tip of Washington, D.C., is the oldest and most urbanized area of Silver Spring, surrounded by several inner suburban residential neighborhoods inside the Capital Beltway. Many mixed-use developments combining retail, residential, and office space have been built since 2004. Silver Spring takes its name from a mica-flecked spring discovered there in 1840 by Francis Preston Blair, who subsequently bought much of the area's surrounding land. Acorn Park, south of downtown, is believed to be the site of the original spring.