Quick answer
The Mission District is a neighbourhood in eastern San Francisco built around Mission San Francisco de Asis, founded on 29 June 1776 and moved to its present site in 1783. It is the city's oldest surviving building. The district escaped the 1906 fire largely because one hydrant on Church Street still had water pressure, and it stays warmer and sunnier than the west side because hills block the fog.
Full transcript
The Hydrant
Corner of Church and Twentieth, at the top edge of Dolores Park, there is a fire hydrant painted gold. In April of 1906 the earthquake broke the water mains under most of San Francisco, which is why the fire that followed did more damage than the shaking did. This one hydrant still had pressure. Crews and residents ran hose from it and held a line here, and the blocks behind it did not burn. That is the reason this neighbourhood still has wooden Victorians while so much of the city is rebuilt in the styles of the decade after. Go and find it. It is repainted every year on the anniversary, and it looks like nothing at all until you know.
Seventeen Seventy-Six
Three blocks away is the oldest building in San Francisco, and it is small and brown and easy to walk past. Father Francisco Palou founded Mission San Francisco de Asis on the twenty-ninth of June, 1776 — five days before the Declaration of Independence was signed on the other coast — and it moved to this site in 1783. That adobe chapel came through 1906 intact. The enormous basilica next to it did not exist then; it opened in 1918. Stand in the gap between the two and look left, then right. Same institution, a hundred and forty years apart, and the small one is the one that survived.
Paint and Sun
The other thing the Mission is known for is on the walls. Balmy Alley off Twenty-Fourth Street has been painted continuously since the nineteen seventies, layer over layer, with older work replaced rather than preserved; Clarion Alley off Valencia is younger and more openly political. Many were made or supported by Precita Eyes, a muralist organisation based in the neighbourhood. And there is a reason people are outside looking at them: the ridge behind the Castro blocks the fog coming off the Pacific, so this district runs warmer and brighter than the avenues. Walk Balmy Alley slowly, end to end, and then come back another year — the point is that it will have changed.