So a while back I printed up the CDC birth statistics (Vital Statistics) for black illegitimacy since 1917, the earliest numbers they have, as far as I could find.
It doesn’t quite fit any full Narrative about black illegitimacy. But the long arc of black illegitimacy is one of racism plus modernity.
There have been multiple fluctuations downwards over 100 years, with the most recent improvement in legitimate births happening since 2009.
And there was a decline during the short window of time in which black men had access to free homestead land before the Depression. There was a further decline as the Great Migration was underway a couple of decades later.
One ongoing pattern is whether teenaged mothers got married. The point at which fewer than half of teenaged black mothers were able to get married was the point at which illegitimacy started shifting heavily upwards. This would have been the 50s or so. And teenaged births being a disproportionate chunk of total births for black women have been a constant. The most recent numbers from 2015 show that black births are nearly 10% teen, while white births are less than 5% teen.
Even more interestingly, in heavily black (20% or more) urban cities like Chicago and Baltimore, teen births are around 25% of births. That is something that probably has some strong explanatory value.