By the mid-20th century, road tripping was an iconic American pastime. A growing middle class meant more people had cars and jobs with paid vacation leave, and Americans used that time to travel with their families to visit sites like Mount Rushmore, the Grand Canyon, and Yellowstone National Park.

The joy of car travel was rooted in spontaneity and freedom. With so many motels and roadside attractions to choose from, all a family had to do was get in the car and start driving, knowing they could figure out where to stay on the fly.

But that wasn’t true for black Americans in the Jim Crow era, during which segregation was legal in the South and practiced just about everywhere else. Most motels, service stations, restaurants, and even public bathrooms were off limits. That meant traveling was more dangerous, more difficult, and definitely less “spontaneous.”

Thanks to a Harlem postal worker named Victor Hugo Green, there was a way for African Americans to know where they would be welcome. In 1936, he published the first edition of The Negro Motorist Green Book, a travel guide for New York City that listed businesses and private homes that would reliably serve African Americans. The book published an updated version each year and eventually grew to cover locations in all 50 states, as well as international locations in Mexico and Bermuda.

The Civil Rights Act of 1964 ended legal segregation, and the Green Book stopped publishing just two years later. Watch the video above to learn more about the Green Book.

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