The commuter rail lines serving the cities of the megatropolis stretch out toward each other, connecting in some spots and reaching tantalizingly close in others. Fortunately, in the two spots where the railroads don’t meet, local transit (and good old shank’s mare) fill the gaps. After contemplating maps of the region, I noticed that it’s theoretically possible to traverse the entire megatropolis using commuter transit (i.e., not Amtrak or long-distance buses.)
The southernmost point is tiny, unincorporated Olive, VA, at the Spotsylvania station of the Virginia Railway Express.
I had to study some regional transit maps to determine the northernmost point - where can you take the train to, and where’s the farthest bus go from there? At first it looked like Hampton Beach, NH was the goal, but I saw that there was only bus service there on Saturdays in the summertime. (And no indications that it's even running in 2023.)
Then I found the bus to Plaistow, NH, which looked like a real contender, but then I noticed that Amesbury, MA is actually farther north, because of that bump around the Merrimack River Valley in northern Massachusetts.
So! My points were set. From the Spotsylvania VRE station in Olive, VA to the Nicholas J. Costello Transportation Center in Amesbury, MA is a distance of 468.9 miles as the crow flies. (Or 535 driving miles, or 562 walking miles, which Google Maps estimates as a 187-hour walk.)
Oddly enough, this straight line passes about 500 feet away from my Queens apartment.
Now the only thing left to do was to take the "theoretically" out of theoretically possible," and do it. The planned trip would traverse nine states and the District of Columbia, and involve eleven transit operators.