A new documentary shows how the real-life Green Book helped black motorists navigate a segregated America

Dr. Donald Shirley (Mahershala Ali) and Tony Vallelonga (Viggo Mortensen) navigate a segregated nation during a concert tour of the American South.

(CNN)In the Oscar-winning "Green Book," the actual Green Book is relegated to a background prop.

African-American pianist Don Shirley's record label gives driver Tony Vallelonga a copy of the book before the two men depart on a concert tour of the Deep South, and we see Tony thumbing through it in brief scenes.
But the movie never really explores what the Green Book is. That's where a new documentary, "The Green Book: Guide to Freedom," comes in. Directed by Yoruba Richen, it details how the real-life Green Book allowed African-American travelers in the mid-1900s to safely navigate a segregated nation.
    CNN spoke to Richen about the book, the hit movie and what people today can learn from her documentary.
    The Green Book was a pamphlet listing safe places to stay and eat for black motorists during the Jim Crow era.

    What was the Green Book?

    "The Negro Motorist Green Book" was a travel guide for African-Americans that was published from 1936 to 1967. It listed services and accommodations where African-Americans were welcome, including hotels, motels, gas stations, liquor stores and hair salons.
    It was published by a black postal worker, Victor Hugo Green. At first, it focused on New York establishments because Green was from the area. Later, the guide's scope expanded as Green gathered tips from readers and other postal workers.

    What areas did the Green Book cover?

    The Green Book eventually grew to a list of more than 9,500 safe havens across the nation.
    While the South clearly demarcated segregation and African-Americans knew where to steer clear, Richen says the Green Book came in especially handy for black travelers outside the South.
    "You really needed it when you were outside the South," Richen said. "The North and West were just as racist, but you needed to know where the places were that would serve you."

    How popular was the book?

    The Green Book was in such demand that it even spread to other countries, Richen said.
    At its peak, Green published 15,000 copies a year. Richen said sometimes families and friends would share one copy and loan it to each other.

    Was the movie's portrayal of Green Book locales historically accurate?

    The Phil Giles Flamingo Club in Michigan offered African-Americans lodging and entertainment.
    Richen said the establishments that Shirley and Vallelonga visit in "Green Book" did not paint a representative picture of the safe havens listed in the guide.
    "The places they went to in the film were really dumps, were very subpar," Richen said. "That's not the extent of what was in the Green Book."
    Richen added, "The places that were listed were some of the finest African-American hotels in the country."
    For example, the filmmakers could have had the characters stay in the A.G. Gaston Motel in Birmingham, Alabama, Richen said. Opened by a black millionaire, the first-class motel was a huge achievement for African-Americans at the time and headquartered Martin Luther King Jr.'s operations for a while.

    What will people take away from the documentary?

    Richen said her film will show viewers how the book helped black Americans go on vacation, despite the risks to their personal safety at the time.
      "I hope that they will really understand what it was like for African-Americans to travel the road of a segregated, racist society," she said. "Despite that, African-Americans pursued recreation and pleasure and created a community."
      Richen believes her documentary also is a way to help viewers to explore the black experience through the lens of entrepreneurship and female business owners.