1900, per NBC's website.
cross country show jumping and dressage
London Olympics
Three Day Eventing was first introduced to the Olympics in 1912, with women being allowed to compete in 1952 - note that the Equestrian events are the only ones where women are allowed to compete against men on equal terms
To win the Equestrian you have to have the most points for dessage,jumping and eventing.
Day 4 of the 2012 Olympics was when NZ got their first medal. it was a bronze won by the NZ equestrian team.
Galen Spencer was the oldest to receive equestrian medal.
Equestrian.
the Olympics (eventing)
Equestrian
Cycling has been competed at the Olympics since the first Modern Olympics in Athens in 1896.
Partial answer: The ages of the riders representing the United States in Beijing are given with their bios on the website 2008 Olympics Equestrian Cheat Sheet, http://www.theequinest.com/2008-olympics-equestrian-cheatsheet/
The first horse's to enter the Olympic was in 776BC in the ancient games, this was the first recorded Olympic event. In modern day Olympics, the first equestrian events (horse events) were held in Hong Kong in 1952.