St. Louis County is one of the most segregated places in America.
On a widely used measure of segregation, it is in the 96th percentile.
In the United States, there are 325 counties and non-incorporated cities (such as Baltimore) that have at least 20,000 people and are at least 20% black. Of them all, St. Louis County is the 12th most black-white segregated, putting it in the 96th percentile.
That figure is based on the latest available census-tract-level data from the American Community Survey, and a metric known as the "index of dissimilarity," a standard measure of segregation. (No segregation metric is perfect, of course.)
The most black-white segregated county, according to this metric, is Wayne County, Mich., home to Detroit. The least: Hertford County, N.C. (St. Louis city, which isn't part of St. Louis County, ranks 21st.)
Here’s another way of looking at it:
About 41% of black residents live in census tracts with populations that are 80% black. The national average: 21%.
In St. Louis County overall, approximately 23% of residents are black. But almost none of county's census tracts come close to that average — most have either far more black residents or far fewer. (Of the county's 199 tracts, just 28, or 14%, fall within 10 percentage points of the average.)
The most segregated areas are much poorer, too.
In census tracts where at least 80% of residents are black, 24% of the population were living below the poverty line in 2012. Just 9% of people in other tracts were.
In the most segregated tracts, the unemployment rate was 19%. In other tracts, it was 7%.
In the most segregated tracts, 58% of households owned their home. In other tracts, it was 73%.
Get the data
The full rankings of all 325 counties with at least 20,000 residents and a 20% black population:
Black–white segregation in St. Louis County ranks 12th among counties and unincorporated cities that have at least 20,000 people and are at least 20% black. An earlier version of this post indicated that the county ranked 15th. The underlying data, and rank percentile, have not changed. (h/t @MonaChalabi.)