In addition to the widening of the Beltway, notice how pavement has proliferated in Fairfax and Loudoun counties in Virginia and Prince George’s and Montgomery counties in Maryland. The District of Columbia was already densely developed in 1984, so the changes there are less noticeable.

The spread of impervious surfaces was widespread across the region, but development was particularly intense along key lines of transportation. Much of the development occurred along the Beltway in communities such as Tysons Corner, Springfield, College Park, and New Carrollton. Inside the Beltway, building followed the Metro rail lines.