4. Philadelphia
Philly looks a bit denser than Chicago near its center in 1950. Definitely by % of population living in high density tracts, though probably not by absolute numbers. Scale is different than Chicago, but it looks like in all directions (North, West and South Philly) is mostly populated by 35k+ tracts consistently. Second densest city core in the country in 1950? The far northern parts of the city were less dense then and now.
Philly's decline looks rather even, though most severe in North Philly, and relatively mild in South Philly. Even today, density drops off quickly right around the city limits: sometimes one of the in between density levels gets skipped without a transition.
5. Boston is the opposite of Philly: much of the older built area is outside of the city limits. Boston looks like it had less high density areas than Philly in 1950, though the peaks were at least as high. South Boston had densities around 50k/sq mile and higher. Large Irish Catholic families? Largest declines were in Roxbury/Dorchester or somwhere on the south side of downtown.
6. San Francisco / Oakland
San Francisco didn't change a whole lot, a few neighborhoods just west of downtown had population declines, a few outer ones grew. Oakland west of downtown (West Oakland) had a population decline; Oakland to the south and northeast of downtown grew a bit. Some spots right near UC Berkeley got much denser.
While San Francisco is similar to Philly/Boston density today, in 1950 it wasn't. Either from less decline but with originally less dense overall housing stock, or being less of a blue-collar city had less overcrowding issues in 1950? Not sure if household size decline would vary by city much, though. Perhaps just more infill, and the outer parts of the 1950 city was less dense than Philly.
