I am in early stages of dreaming of another long trip - this time with a theme of visiting US state capitols in the lower 48.

For planning purposes, I put in a Google Maps route that gave me 13875 miles to visit state capitol buildings in the lower 48. Not the absolute minimum distance I could find but enough in a range to compute a time budget and to cross check seasons. However, I wouldn't actually use Google Maps bicycle directions (for several reasons) but instead get my own routing using a combination of investigating maps, existing routes and Strava heat maps...

Hence, this post that is more specific to the Washington DC to Boston corridor to solicit any ideas to investigate. In particular, image you wanted to bicycle the following segments:

Washington DC to Annapolis
Annapolis to Dover
Dover to Trenton
Trenton to Hartford
Hartford to Providence
Providence to Boston

This goes through a somewhat dense populated area with ~50 million in the total metro areas (e.g. Washington, Baltimore, Philadelphia, New York, Boston). I'd want to look for some routes didn't go too far out of the way but also were OK for cycling. I did the Atlantic Coast some years ago including going through NYC and lived in Boston so I have seen some of this before. Any thoughts or suggestions of route areas or cycle corridors that get me to where I want to go?