William Gargan's older brother, Edward Gargan, was also an actor.
When he died, William Gargan was on a flight from New York to San Diego.
Early in his career, William Gargan sold bootleg whiskey to speakeasies in New York. He worked with Dave Chasen, another young actor, who would go on to open the famous Brown Derby restaurant in Hollywood.
Before working as a private investigator, William Gargan worked as a credit investigator and collection agent for a clothing company. On one trip to collect an overdue payment, he was shot at by the customer.
William Gargan's father was a bookmaker, exposing Gargan at a young age to a number of shady and interesting characters from all walks of life.
William Gargan's radio contract for Barry Craig with MCA was a seven year deal worth one million dollars.
In what turned out to be good practice for his roles as TV and radio private eyes, William Gargan worked as an investigator for a New York firm for $10 a day, plus expenses. He ultimately lost the job when a suspect he was trailing eluded him.
William Gargan's autobiography, Why Me?, was published in 1969.
William Gargan was nominated for the 1941 Academy Award for Best Supporting Actor for his performance in They Knew What They Wanted.
William Gargan won the Screen Actors Guild Lifetime Achievement Award in 1967.
William Gargan's salary for Martin Kane, Private Eye was $4500 per episode.
William Gargan: (on the end of "Martin Kane") The show began to slide downhill. In desperation, I began to mug a little more, to cover up the new holes, and the script writers began to write more blatantly. You get into a terrible rut this way. Everybody works harder to undo the damage, and the result is more screeching, more overacting, overwriting, which starts to drive the viewers away and to get them back you come up with more and more desperate gimmickery.
William Gargan: (on "Martin Kane") We gave the audience a good time, and if all the threads were not tightly tied in a half-hour, we swept them under the bed. Have fun. And the show, for whatever reason, took hold. The show had charm, and its charm held together the lunacy, the feeble character development, the limited camera work.
William Gargan: (on his TV role of "Martin Kane, Private Eye") Very soon in the game, I realized our stories were nothing to rave about. How much well plotted story line and genuine character development can you accomplish in a half-hour? So I made the program a showcase for me. After all, that was what we were selling - Martin Kane. I developed a tongue-in-cheek style, a spoof of the hard-boiled detective, a way of silently saying, "Don't blame me for the lousy stories, I didn't write them. And anyway, what's the difference? Relax."