It may be called "Oktoberfest," but the big event starts in September. It all began with a wedding—in October 1810. On the 12th day of October that year, Crown Prince Ludwig (later King Ludwig I of Bavaria) wed Princess Therese von Sachsen-Hildburghausen and held a big party near Munich (München). It was so popular, that the party (complete with horse racing) took place again the following year, prompting the start of a traditional German celebration that has become world famous. Other than for interruptions caused by war or disease, Oktoberfest has been celebrated every year since 1811.
Oktoberfest will celebrate its 200th anniversary in 2010. Although the horse racing (Pferderennen) didn't become a lasting part of Oktoberfest, just about everything else did! Today, the world's most famous beer festival (das Bierfest) is held on a large 31-hectare field in Munich known as die Theresienwiese (named for Princess Therese) or just die Wiesn if you're a local.
Happy Beer Fiesta!