Before Rin Tin Tin there was Strongheart, a former German police dog who became a canine star of Hollywood silent films. According to Strongheart's IMBD page, the dog was originally called Etzel von Oringer and was carefully bred. Described as fearless, Strongheart served in the German military in WW1 before being discovered at age three by American director Laurence Trimble in 1920. A year later Strongheart made his movie debut in "The Silent Call".
Strongheart arrived in Hollywood with the sharp instincts of a K9 and had to be socialized to be around people. Eventually the dog's German police training was tamed but his natural instincts had a reputation for "sniffing out people with bad intentions". Strongheart was known for suddenly pursuing people who turned out to have criminal records or a violent history. Once a police dog always a police dog.
A succession of films followed Strongheart's debut but it was an accident on a film set that ended his life at 12. After being burned by a studio light, Strongheart died of his injuries. Like Rin Tin Tin, Strongheart's descendants are still alive today. Wikipedia lists the location of Strongheart's star on the Hollywood Walk of Fame at 1724 Vine Street.