The first Oktoberfest was held in Munich on October 12, 1810, and it was a wedding, not a beer festival. Crown Prince Ludwig of Bavaria married Princess Therese of Saxe-Hildburghausen, and the people of the city were invited to the fields outside the walls for a horse race and a fair to mark the day. The meadow was named Theresienwiese, after the bride, and the wedding was largely forgotten. The festival kept the ground and the name and never went away.
The horse race was central. A cavalry officer ran it. He wanted the day to look royal. It was run in front of the royal family, and the day ended with the city's marksmen and the national guard putting on a display. A year later the city repeated the fair. A cattle show was added, because someone had to pay for it, and from there the thing grew by itself, year by year, through war and revolution, though the horse race disappeared in 1960.
The beer came later. Small stands selling beer and food appeared in the early years, and by the late nineteenth century the brewers of Munich were building the halls, and the roast chicken, and the rides, and the brass bands, all of it had collected on the same meadow. It runs now for about sixteen days from the middle of September to the first Sunday in October, a schedule moved earlier so that the evenings would be warm, which is why the festival called October sits mostly in September.
The numbers are the size of a city. Roughly six million people come in a normal year, most of them from Bavaria itself, and the beer served is brewed inside the city to the strength the festival has always used, and the tents are run by the same families in some cases for a century. Munich has cancelled it for war, for cholera and, twice, for the pandemic, but the ground is the same field the prince's bride gave her name to in 1810.