I recently finished listening to this wonderful podcast episode from 99% Invisible about something called The Green Book which helped African Americans travel the United States in safety during the era of Jim Crow laws.
The book was published by Victor Hugo Green who gathered data from establishments all across the US thanks to the trusty community of black US Postal Workers. Green was also a postal worker and he knew that the people who would know communities the best would be the very people who delivered mail. These folks would know whether restaurants or hotels would allow blacks and would be able to tell Green whether they were friendly at all or hostile.
The Green Book was published, every year, until about 1966. It's demise is mostly due to the passage of the 1964 Civil Rights Act which made discrimination on color, sex, religion, or national origin illegal.