This is what we found on Wikipedia regarding the My Darling Clementine:

My Darling Clementine is a 1946 American Western film directed by John Ford and starring Henry Fonda as Wyatt Earp during the period leading up to the gunfight at the O.K. Corral. The ensemble cast also features Victor Mature (as Doc Holliday), Linda Darnell, Walter Brennan, Tim Holt, Cathy Downs and Ward Bond.

The title of the movie is borrowed from the theme song "Oh My Darling, Clementine", sung in parts over the opening and closing credits. The screenplay is based on the biography Wyatt Earp: Frontier Marshal by Stuart Lake, as were two earlier movies, both named Frontier Marshal (released in 1934 and 1939, respectively). The book was discovered to be highly inaccurate and Wyatt had told many outright lies about himself, his brothers and the events surrounding the O.K. Corral incident to both Lake and director Ford.

My Darling Clementine is regarded by many film critics as one of the best Westerns ever made. In 1991, the film was deemed "culturally, historically, or aesthetically significant" by the Library of Congress and selected for preservation in the United States National Film Registry. It was among the third annual group of 25 films named to the registry.