For Black travelers driving across segregated America in the 1940s, ’50s and ’60s, the The Negro Motorist Green Book was more than a travel aid – it was a guide for keeping them safe.

The Green Book – named after its creator, not the color of its covers – was pocket-sized, about 5 by 7 inches, and published nearly every year from 1937 to 1966.

The guide was an indispensable list of Black-friendly businesses essential to travel: hotels, restaurants, gas stations, garages and more.

"It was one of many things African Americans had to develop to survive a hostile environment," says Scot Brown, professor of African American Studies and history at the University of California-Los Angeles. "A modern-day equivalent could be a Black GPS."

African Americans of that time were restricted by Jim Crow laws, harsh legislation passed in Southern states that limited rights of Black people from 1877 to the mid-1960s.

Those laws promoted white supremacy in every aspect of daily life, including travel. White-owned businesses could legally turn away Black travelers seeking a meal, a room for the night or even a restroom. Those who protested risked horrific violence or worse.

"They were a series of laws designed to impose segregation," Brown says. "They restricted voting rights, limited access to mobility and controlled Black bodies, turning them into a pliant labor force."

The Green Book was in response to Jim Crow.

It was created by Victor Hugo Green – reputedly named after Victor Hugo, French author of "Les Misérables" and other works – a Black postal worker and entrepreneur in Harlem who saw the need for a guide.

The guide was established in 1936, but "there's no known copy of a 1936 edition," Maira Liriano of the Schomburg Center for Research in Black Culture, part of the New York Public Library, told USA TODAY.

"Some have suggested that the Green Book was established in 1936 but that 1937 was the first printed guide," Liriano says. "There is no way to know for sure."