The Valentino Memorial Service is the longest-running annual event in Hollywood. The Easter Sunrise Service at the Hollywood Bowl started a few years earlier but, although it's currently running, it had been suspended for a few years. The Valentino Service continues unabated, with no breaks since the first one in 1927.
A big part of what sustained it in the earlier decades was the mysterious "Lady in Black" element which drew folks who were curious to witness that strange tableau. The tone of it in the modern era is more of a "history conference" - although there is a Lady in Black to represent that intriguing part of the Valentino myth. The entire history of the event is detailed in "Valentino Forever," which gives a year-by-year overview of the happenings and the "kooks" the event attracts (one of which is now me, obviously). Tracy Terhune, author of the book and one of the organizers of the event, is the grandson of the late cowboy star, ventriloquist, and Magic Castle member Max Terhune.