By The Associated Press

PASADENA, Calif. (AP) — Historian Henry Louis Gates can trace the roots of his upcoming PBS documentary about the Reconstruction to his days in school.

That’s when he heard about the end of slavery during the Civil War followed by virtually nothing about race relations until the civil rights movement in the middle of the 20th century.

“Freedmen Voting in New Orleans,” 1867, engraving courtesy of New York Public Library Digital Collection

The Harvard historian said it led him to wonder why a civil rights movement was necessary a century after the Emancipation Proclamation.

His answer arrives on April 9, when PBS will premiere the first half of his four-hour documentary on America after the Civil War. He hopes it will enlighten people to what he believes is one of the least understood periods of the nation’s history.