Collection: Washington, D.C.

Washington, D.C. sits at the boundary between the ancient crystalline rocks of the Piedmont and the younger, sediment-rich Atlantic Coastal Plain, a transition that strongly influences the region’s topography and soils. The city’s landscape reflects hundreds of millions of years of tectonic activity, erosion, and sea-level change, with rivers including the Potomac carving through resistant bedrock. These geologic contrasts shape everything from local building stone to groundwater flow and floodplain development.