Joan Crawford always considered The Unknown a big turning point for her. She said it wasn't until working with Lon Chaney in this film that she learned the difference between standing in front of a camera and acting in front of a camera. She said that was all due to Chaney and his intense concentration, and after that experience, she said she worked much harder to become a better actress. Director Tod Browning loosely based the story on a real event of his circus days, where a man masqueraded as an acrobat to evade the police. As Paul Desmuke was born armless, he doubled for some shots of Chaney where Desmuke used his feet for smoking or playing a fiddle.

For many years, this film only existed in murky 9.5mm dupes on the black market. In March 1973, at a screening of this film at George Eastman House, archivist James Card said that Henri Langlois and his staff at the Cinematheque Francais discovered a copy of it in 1968 among other miscellaneous cans of film marked "l'inconnu" (films "unknown" due to missing titles, etc.). In 2012, director Guy Maddin named this one of the ten best films ever made in the decennial Sight & Sound Directors Poll of the Greatest Films of All Time. Included among the '1001 Movies You Must See Before You Die', edited by Steven Jay Schneider.