What’s interesting to me about East Boston is the fact that there are so many abutting multi family dwellings that are made of wood. Usually, at least in Boston, you get two family homes, then separate triple deckers and then the next level up is either stone-clad triple deckers, or stone- or brick-clad townhomes that abut each other. There’s really nowhere else in Boston where you get long streets like Chelsea St, with a continuous wall of wood (now aluminum or vinyl) sided houses. I think in other cities you see this (I’ve certainly seen walls of what I’d call 2 story triple deckers in Brooklyn that are abutting, I think Baltimore and Philly also have abutting 2- and 3-family houses). But for Boston this is unique. The idea that East Boston was developed slightly later maybe holds some truth but there must be other factors. The book Streetcar Suburbs really gets into very specific details of housing stock and might be one place to look, off the top of my head I don’t remember if it mentions East Boston.