St. Louis City (61 square miles, 319,000 in yellow )
St. Louis County (508 square miles, ~1 million everything else )
So in 1876 St. Louis City was one of the fastest growing cities in the States and St. Louis County was farmland. The City saw no use for it, wanting to keep their resources and money for themselves split from the County in what is known as 'The Great Divorce'.
The two are still divorced today.
So up until 1950 all through The Great Migration, The City continued to grow reaching its peak at 857,000.
It always had murders, and the italian mob at one time too, but a densely populated city with resources and services. The 4th largest City at its peak.
Then 3 things happened.
1. The end of WW2 and the G.I. Bill which Black Vets never got. 1946.
2. The landmark supreme court case
Shelley vs Kraemer which ended racial housing covenants. That happened here. 1948.
3. The opening of the interstate system, which also started here. 1956.
So over the next couple of decades the city experienced massive white flight to the suburbs.
The 80's- 90's brought the crack era so you had a black middle class flight out of the city and into the county suburbs.
So the city, still 61 square miles, had its tax base gutted, and remained violent, but now violent, forgotten and disenfranchised. Majority black (~ 50%)
As of today the city is in flux, billions are being poured into the central corridor (east-west). South city neighborhoods are starting to gentrify. None of that investment has spilled north though (delmar divide) except for the NGA - into a mostly empty part of land where the infamous Pruitt-Igoe Projects once stood.