The two songs "76 Trombones" and "Good Night My Someone" are the same tune, played in different tempos. Meredith Willson used this technique to present a masculine and feminine slant on the events surrounding Harold Hill's arrival in River City and his budding relationship with Marian.
Despite Robert Preston's Tony-award winning performance in the Broadway production, Warner Bros. executives wanted a bankable star in the lead role of Professor Harold Hill for the movie. According to Shirley Jones, Frank Sinatra was offered the part, but Meredith Willson insisted on Preston and threatened to pull the movie rights. Cary Grant was also approached, but told the Warner Bros. executives, "Not only will I not star in it, if Robert Preston doesn't star in it, I will not see it." Preston got the part, and the movie was a big success, despite Warner Bros' misgivings.
Meredith Willson made more income off The Beatles' version of his song "Till There Was You" than he did off the play and the movie combined.
The marching bands of the University of California and the University of Southern California were drafted in for the final parade scene.
Shirley Jones was pregnant during filming. Costume designers had to adjust her dresses several times to conceal the pregnancy. When she and Robert Preston embraced during the footbridge scene, her unborn baby, who would be named Patrick Cassidy, kicked Preston. Years later, when Cassidy introduced himself to Preston, the actor told him, "Yes, we've already met."
Rance Howard: Oscar Jackson, a man stopped in the street by Marcellus Washburne as the angry townspeople begin the search for Professor Hill.