Well, La Marmotte in France started in 1982... and I know you have apparently been cycling since before the bicycle was invented, but this is older than a lot of people who are posting on this board, and there are a few scattered around the world that are earlier than this.
The first Dragon Ride was in 2004. It was so good, the UCI classified it in 2005.
In 1997, I went on a bicycle event at Donington Park Motor Racing Circuit. It was during National Bike Week and was raising money for cycling charities in Leicestershire. Anyone could attend. As it was on a closed road, there were no age, speed or type of bike restrictions.
Attendees could give a few quid and ride round as much as they wished. For a few quid more, race boys, Wannabes and club members could get a number allocated and a marshal would clock the rider each time he/she crossed the start/finish line.
I rode the forty miles to Donington, rode 10 fast laps at race pace with members of Hinckley, Coalville and others ( 2.5 mile laps ), and then rode home to cool down.
In the last couple of laps, we became one big group as it had sucked up lone riders and the marshals were having a real game clocking the numbers. Marshals round the course were cheering as if we were racing.
There were no medals or prizes, just a thoroughly enjoyable day out.
Subsequently, I have ridden a Sportive. Not a patch on the Donington event and not worth doing another.
I ride Audax now and to my mind, a Sportive is an Audax with official timing and the route neatly marked out.