Institutional racism aka Jim Crow laws.
There's an excellent book which explains in detail how neighborhoods became segregated because of federal policy and laws:
"The Color of Law: A Forgotten History of How Our Government Segregated America" written by Richard Rothstein
After WWII, there was a severe shortage of housing so the federal government helped create millions of new homes.
The federal government designated a block as "white only" or "black only". There were many situations in which a white family lived for years in a house on a newly designated black-only block. White families sued to stay, but eventually lost their cases and were forced to move.
There are also race covenants in most white-owned homes' deeds that state it's illegal to sell their house to a black family which was enforceable for decades. If you have an old deed, I suggest you read it because the racist language is still there.
There were thousands of policies and laws created across the country, with federal support, to segregate America.
re: black universities. It was illegal for African-Americans to attend most if not all colleges and universities so they created their own.
Chopper: I'm just a bloody normal bloke. A normal bloke who likes a bit of torture

Why do America have Black only Communities
Huh??? WTF???
Get a grip, Benny!
What century are you living in?
You asked a pretty question; I've given you the ugly answer.
Fasten Your Seatbelts….
It's Going To Be A Bumpy Night!

Because they have white only Hispanic only Asian only and other only communities. Why do you keep asking stupid questions?
My password is password.

Because the amount of income separates us.
How you die does not redeem how you lived. - A black pastor on the life and death of Charlie Kirk

White people are on your mind 24/7 and your thread topics prove it.
Chopper: I'm just a bloody normal bloke. A normal bloke who likes a bit of torture

Why the **** are you so fascinated by Black people?
You don't even like blacks. You don't listen our music, or watch our movies, or any of our artforms….
Why do you care that we had to make our own college/university?
Put a muzzle on Tits Malone, PI

I'd like to see sheetsadams thoughts on that very informative and awesome post.
Chopper: I'm just a bloody normal bloke. A normal bloke who likes a bit of torture

Institutional racism aka Jim Crow laws.
There's an excellent book which explains in detail how neighborhoods became segregated because of federal policy and laws:
"The Color of Law: A Forgotten History of How Our Government Segregated America" written by Richard Rothstein
After WWII, there was a severe shortage of housing so the federal government helped create millions of new homes.
The federal government designated a block as "white only" or "black only". There were many situations in which a white family lived for years in a house on a newly designated black-only block. White families sued to stay, but eventually lost their cases and were forced to move.
There are also race covenants in most white-owned homes' deeds that state it's illegal to sell their house to a black family which was enforceable for decades. If you have an old deed, I suggest you read it because the racist language is still there.
There were thousands of policies and laws created across the country, with federal support, to segregate America.
re: black universities. It was illegal for African-Americans to attend most if not all colleges and universities so they created their own.

Why does Ausfailia have all-aboriginal communities? And all-Chinese communities? And all-Lebanese communities?

None of them are entirely black. In fact, West Virginia State University is classified as a historically black college and it's enrollment is more than 70% white. It's merely a historical designation.
That's an unsatisfactory superficial Google interpretation about something which you know absolutely nothing about.
If there is an abnormal high white student population at college/university created specifically for African Americans, the reasons for that anomaly is that HBCU has something very valuable that the white students are after….
So what happens just like with anything belonging to a different race or ethic culture,
WHEN the white man desires it, he will slowly take it over while preventing the rightful owner access
.
The non blacks get accepted under AFIRMATIVE ACTION POLICIES.
Yeah…ironic isn't it?
I have friends that graduated from an HBCU. The faculty there has basically stated that. So I'm not race baiting or proving ingredients misinformation in order to confuse folks.
I'm telling you the truth of the situation.
Put a muzzle on Tits Malone, PI

None of them are entirely black. In fact, West Virginia State University is classified as a historically black college and it's enrollment is more than 70% white. It's merely a historical designation.
These colleges are almost all located in the south, where segregation was a thing until the '60s and these were the only options for black students. There was one famous incident where the governor of Alabama attempted to block black students from enrolling at University of Alabama. You've seen Forrest Gump, right?
Draft Barron Trump

Only happens in America though, black collages.
Chopper: I'm just a bloody normal bloke. A normal bloke who likes a bit of torture

We don't. There are communities that are predominantly black (and others that are predominantly white, Latino, Asian, etc), but anybody is free to live anywhere they want.
And historically black colleges are just that: colleges initially founded to serve black students, at a time when they weren't always welcome on other campuses. As of 2020, around 25% of students at these colleges weren't black.
Draft Barron Trump