The oldest building in San Francisco — the adobe church at Mission and 16th built by Anza expedition settlers in 1776 — turned 250 on Saturday. Anza descendants held their annual ceremony in the Presidio. Ramaytush Ohlone descendants called the same date a day of mourning.

At 16th and Dolores on Saturday morning, the 250th anniversary of San Francisco arrived in two registers at once.

On June 27, 1776 — seven days before the Declaration of Independence was signed 3,000 miles to the east — a party of 30 soldiers, their wives, and more than 100 children reached the banks of a tule-grass lake they called Laguna de Dolores, after a 1,200-mile march from Sonora under the command of Spanish Lt. Col. Juan Bautista de Anza. The settlers were of Mexican, African, Indigenous and European blood, and by most accounts fairly poor: recruited with a promise of land they couldn't own at home, according to NBC Bay Area's Joe Rosato Jr. Two days after arriving, they held a mass beside the lake. Many historians count that ceremony as the unofficial founding of San Francisco.

The adobe-and-redwood-timber church they built afterward, Misión San Francisco de Asís, still stands at Mission and 16th Streets. It is the oldest existing building in the city.

Every June 27, members of Los Californianos — a group of Anza expedition descendants — gather in the Presidio to read the names of those who made the march. This year the 250th brought more intention to the ceremony: flowers were placed, descendants stood, horses came. Lance Beeson, a descendant of Lt. José Joaquin Moraga who guided the expedition's final leg through California, told NBC Bay Area his ancestors were seeking what their home regions couldn't provide. "They didn't have a chance to own land where they were recruited from," he said.

Three blocks north of Mission Dolores, near the intersection of Camp and Albion Streets in the Mission District, a plaque marks the site of that first mass. Walk by today and it sits in an ordinary block of the neighborhood — easy to miss between the foot traffic and the parking and the sun on the pavement.

What the 250th holds in tension: Gregg Castro, of the Ramaytush Ohlone, told NBC Bay Area this week that his people occupied the land in what became the Presidio long before the expedition arrived. "This is not a celebration for us," he said. "This is a remembrance of when the dark years began for us." The mission's founding drew Ohlone people into labor under Catholic conversion; within years, Castro said, many of his people "were already enslaved" and their language, songs, rituals, and ceremonies were largely erased. Almost none of the Ramaytush language survives.

The adobe walls at Mission and 16th have stood 250 years. The ground beneath them is considerably older.