DC and Baltimore are typically lumped in as one metro area.

https://en.wikipedia.org/wiki/Baltimore%E2%80%93Washington_m...

Not really: "It is composed primarily of two major metropolitan statistical areas, the Washington–Arlington–Alexandria, DC–VA–MD–WV MSA and the Baltimore-Columbia-Towson, MD MSA. In addition, six other smaller urban areas not contiguous to the main urban area but having strong commuting ties with the main area are also included in the metropolitan area."

I mean some people talk about the Northeast megalopolis. https://en.wikipedia.org/wiki/Northeast_megalopolis Boston, New York City, Philadelphia, Baltimore, Washington DC, and some times Richmond. But, that does not mean Boston and DC are somehow the same city.