Three jurisdictions mean three content sets, not one service area page
A dealer selling across the metro is running three local search programs at once, and one page listing twenty city names does not serve any of them.
The District, suburban Maryland and Northern Virginia license trades, tax and permit separately. Google does not know that, but your buyers do, and so does the ranking algorithm through sheer proximity. Results shift as the searcher moves across the river or up Georgia Avenue.
Build a genuine page for each jurisdiction where you actually hold a license and pull permits. Not a template with the place name swapped. Each one should say what you do there, what a permit generally involves in that jurisdiction, and how your crews reach the work. Requirements differ across the District, Montgomery County and the Virginia jurisdictions, and current rules are worth confirming with each building department.
The ranking gain is real but secondary. The bigger return is that a page stating plainly which jurisdictions you cover stops inquiries you cannot serve. A Virginia-only dealer ranking for Bethesda searches is paying in wasted phone time.
Publish the reverse too. If you do not work in Prince George's County, say so somewhere findable. It costs you nothing and it saves an estimator a morning.