When is San Francisco’s real birthday?

San Francisco celebrated a big birthday on Wednesday, marking a 170 years since its founding. Or did it? It turns out there’s some potential for dispute about when San Francisco truly became San Francisco.

It’s true that the modern city of San Francisco first incorporated on April 15, 1850 (hence 415 Day). Many people on social media—among them columnist Heather Knight, Supervisor Matt Haney, and the staff of the San Francisco International Airport—wished the city a happy birthday.

But at least a few residents took exception to this and proposed that the city’s true anniversary is another date. Who’s right? Well, arguably they all are—from a certain point of view.

What people consider San Francisco’s real birthday will tell you a lot about what they think about the history of San Francisco. Consider the following:

• 740 CE: The modern Presidio Trust says that there’s archaeological evidence of Ohlone villages in the area dating back at least this far. But without any records of those periods we’ll never know precisely when the first person settled on the windswept peninsula that we now call San Francisco.
• June 29, 1776: On this day, Juan Bautista de Anza’s expedition raised the first Presidio at the mouth of the Golden Gate and established European colonization of the Bay Area. The Spaniards founded the Misión San Francisco de Asís the same day, and that building endures, though the original Presidio lasted only a few years before being replaced. It turns out adobe architecture and dense fog were a tricky combination.
• June 25, 1835: For decades there wasn’t much else around except for the Presidio and the Mission, and it took until 1835 for someone to create the first independent residential homestead in what would one day become San Francisco. William Richardson, a British sailor who visited the Presidio in 1822—who partied so hard that he never wanted to leave—built the first home in the future SF on this date. That domicile was little more than a tent, although over the next year Richardson replaced it with a wood house, and later a larger adobe. A plaque on Grant Street in Chinatown marks the location of the original structure.
• January 30, 1847: Within a dozen years, the village of Yerba Buena grew to a few hundred people and was now nominally an American holding, although California wouldn’t become an official U.S. territory until the conclusion of the Mexican-American war the following year. On this day, Yerba Buena’s chief magistrate, Washington Bartlett, issued an order changing the town’s name to San Francisco to correspond with the bay and “to prevent confusion and mistakes,” crossing the meridian from the proto-San Francisco to the real deal.
• February 18, 1850: By this point, California was well on its way to being a state, with SF’s population was growing by the tens of thousands every year. California’s first constitutional convention, inaugurated the previous year, recommended the creation of 27 counties, which, on this day, the new California legislature officially established, San Francisco County among them. Also founded: Napa, Contra Costa, Santa Clara, Marin, and Sonoma counties.
• April 5, 1850: The day the legislature voted to incorporate San Francisco as a city. The official incorporation didn’t happen until ten days later, at which point the first city charter went into effect. California joined the union as a state less than six months later.

So which of these anniversaries is the real deal? It all depends on precisely what we mean when we say “San Francisco” and how closely we expect history to resemble that meaning.

In a certain sense, San Francisco is reborn every time people’s expectations about it change, meaning that almost any day might mark a new phase in the life and times of the city by the bay. But if that’s too abstract for you, any hard benchmark in the history books is probably as good as another—after all, in the end, they all wound up part of the same place.