The Treasure Island referred to in the title is a man-made island in San Francisco Bay that was built in 1936-37 in anticipation of it hosting the Golden Gate International Exposition of 1939-40. After the fair closed, the U.S. Navy used the site for many years. Since the 1980s the site has been used by many film and television production companies with aircraft hangars #2 and #3 converted to sound stages.
In the beginning of the movie on the plane, Jimmy Chan (Victor Sen Yung) informs the insurance actuary he's age 20 going on 21. The actuary says according to his figures he can expect 45.16 more years of life, barring a fatal accident. He walks away, looking troubled. In real life, Yung indeed died at age 65, in a natural gas poisoning accident.
It is believed that this film may have partially inspired the "Zodiac Killer" in the San Francisco area during the late 1960s, due to the Cillian of the film being named "Dr. Zodiac" as well as sending letters to San Francisco.
The 22nd of 47 Charlie Chan movies.