The original maps were smaller. The later maps have routing info, which makes them bigger. The Roam has 2 GB, which is thin. So, the "map database management" isn't hard to understand.

The California map is 240MB (it appears). There should be enough room for the three regions (VA, MD, DC) you need. Presumably, you deleted all the maps (including those for other continents) you aren't using.

While there's less of a need for it now, for the Garmins, one can install free maps covering a custom region. Where this is still useful is getting more up-to-date maps.