Howard had started working on the movie in 1994, Entertainment Weekly reported.
"I wanted to turn Harriet Tubman's life, which I'd studied in college, into an action-adventure movie. The climate in Hollywood, however, was very different back then," Howard said, according to CNN. "I was told how one studio head said in a meeting, 'This script is fantastic. Let's get Julia Roberts to play Harriett Tubman."
Howard did not say who the executive was in the Q&A session published by Focus Features, the studio that released the movie "Harriet" this month, but he said the person fired back when someone said that Roberts couldn't be cast as Tubman, "It was so long ago. No one is going to know the difference," CNN reported.
Howard's screenplay was eventually turned into the movie "Harriet" which is in theaters now and stars Cynthia Erivo as the freedom fighter, along side Janelle Monáe, Leslie Odom Jr., Jennifer Nettles, Joe Alwyn and Clark Peters.
Click here to read Howard's complete interview.