For African-American travelers in the Jim Crow-era South—often journeying from the north to visit relatives who had not joined the Great Migration—an unprepossessing paper-bound travel guide often amounted to a survival kit. The Green Book often functioned as a lifesaver.

Visionary publisher-entrepreneur Victor Green, a Harlem postal carrier, introduced the travel guide in 1937. For blacks denied access to restaurants, hotels and restrooms—and who often risked even greater danger if they were driving after dark—it was an essential resource, listing hundreds of establishments, across the South and the nation, that welcomed African-Americans.

Before the 1964 Civil Rights Act outlawed segregation, the Green Book sold in the millions and was passed from family member to family member. For those who relied on it, it amounted to an essential safety precaution. Today, it is a potent artifact of discrimination.

The Green Book is also the subject of filmmaker Ric Burns’s forthcoming documentary. Burns is exploring the Green Book as a window into history, and into the present, where the experience of driving while black is again at the center of our national conversation. I spoke with Burns about what he’s learned so far in making this film.