OK, first a correction to the tag posted on this movie's main page. Abe Lincoln did not walk with his sister in the movie, nor did he stop at his sister's grave. The individual in question is Ann Rutledge who was a very close friend to Lincoln in his New Salem days. Some say that Ann was, in fact, Lincoln's girlfriend, but there is no evidence to support it.
Now, there are fabrications and fictionalizations in this film. Hollywood has always taken dramatic license with anything under the sun, and "Young Mr. Lincoln" is no exception. However, the courtroom case that is in the film is based on a real event: the accusation of murder against William "Duff" Armstrong, and even though it's largely fictionalized in this film with lots of name changes, it will still have viewers riveted to the screen. This is Hollywood's Golden Age, with drama at it's finest, and Henry Fonda gives possibly the best Lincoln played by anyone.