William Wrigley, Jr. bought 99% of Catalina Island in 1919. He chose the setting for his new home on Mt. Ada (named after his wife, Ada) because it received first sunlight in the morning and the last rays at sunset. The Inn is 350 feet above the town and harbor. The building of the Wrigley's home was started in 1920 and completed in 1921. The couple enjoyed their home together through January 1932, when Mr. Wrigley died. Mrs. Wrigley continued to visit until 1947, when she suffered a stroke and lingered in a coma in Pasadena for 11 years. She died in 1958. From 1921 to 1932, the Wrigley's entertained a number of famous guests at their island home, including Presidents Calvin Coolidge, Warren Harding, and the Prince of Wales.
Mr. Wrigley also owned the Chicago Cubs professional baseball team, and invited them to hold their spring training on the island. Following Mrs. Wrigley's death, the home was owned by the Santa Catalina Island Company and used as a tourist attraction. In the 1970's, the home was given to the University of Southern California to be used as a conference center. In 1985, the present innkeepers secured a long-term lease of the property and created the successful business known today as The Inn on Mt. Ada. For the past 18 years in a row, the Inn has been awarded the Mobil Travel Guide 4-Star rating, a rating awarded to only the top 2% of lodging properties in the entire US & Canada.