The Census maps Silver Spring as a Census-designated place, not a municipal-boundary finding. Its current mapped land lies in Montgomery County and its edge touches, but does not extend into, Prince George's County. That describes the CDP footprint—not the county or municipality for a particular house. Verify an address in official records rather than relying on its mailing label.
Montgomery County uses several Silver Spring planning and service-area names, including Downtown Silver Spring, Four Corners, Eastern Silver Spring, Long Branch, Forest Glen/Montgomery Hills, Kemp Mill, and Lyttonsville. These labels help orient you, but they do not establish that a parcel belongs to a specific plan or service area. Montgomery Planning describes downtown as a hub for surrounding residential communities, with shops, restaurants, offices, and civic uses.
Census Silver Spring CDP map · Montgomery County Silver Spring Regional Services · Montgomery Planning: Silver Spring