US Route 1 - can you walk it?

No, but it would be interesting to drive. Only part is now interstate; some is still highway / state road or unrestricted road way. Given the variety of route types and neighborhoods and what all, even driving could be an adventure.

I’m not sure about the reliability of the results, but there’s a feature on Google Maps for selecting ‘walking’ as the mode of travel between any two points.

Just goofing around, I recently played with it to see what it would say about hiking from L.A. to Flagstaff, Arizona.

It managed to find frontage roads and other curious byways that would keep a hiker safely off the interstates. (But my particular hike wouldn’t be terribly feasible. Beyond the other desert conditions to be expected, there’s one or more stretches of 100 miles or so between grocery stores. There might be ways to deal with that, but… it’s just idle speculation anyhow.)

I’m just sayin’ it was kind of an interesting thought experiment. You might try it for your route.

But not with sufficient detail to be able to tell exactly where the old roadway was, nor what streets it followed through cities and towns. There will be places where new bridges have been built, and then the old ones demolished.

There is a Wikipedia page for the section of US-1 in each state that it passes through, which contains a wealth of historical information that will be useful reading to anyone considering such a trip.