My first encounter with black only facilities was at a Greyhound bus stop; I had to go so bad, and I couldn't believe my ears when I was told I couldn't use the men's room right outside the front door but had to go inside and stand in Line.
On the way out, a guy was leaving the outside stall and I asked him what it was all about; the grizzled, old black gentleman said, "Son, you'll learn soon enough..."
I believe Professor Thomas Sowell tells a similar story about a trip through North Carolina during his service as a Marine during the Korean War. As I recall, in his autobiography
A Personal Odyssey, he relates an incident at a bus stop wherein he got involved in a bit of an altercation, which got him into trouble with the authorities.