This was a bold movie and one of the few to depict interracial marriages in a positive. It became a classic and is a must watch. In 2017 (on its 50th anniversary), the film was selected for preservation in the United States National Film Registry by the Library of Congress as being "culturally, historically, or aesthetically significant"
https://en.wikipedia.org/wiki/Guess_Who%27s_Coming_to_Dinner