Why not look at the event that was the "mother" of all the commonly known ones today, like the Tour de France: The Paris-Brest-Paris.

http://www.randonneurs.bc.ca/pbp/history.html
http://www.rusa.org/pbp.html
http://www.rusa.org/pbphistory.html
http://www.machka.net/pbp/machka.htm
http://en.wikipedia.org/wiki/Paris-Brest_et_retour