SFGov TV, the SF city media arm, has a running web series called QuickBites, and they've just done a piece on the Mission-style burrito that makes some highly spurious claims.
The big falsehood: The original type of burrito found in Mexico didn't have rice and beans in it at all, as the little diagram in the video suggests. The Mission burrito has that stuff, along with guac and sour cream, but the real, OG burritos were just meat, cheese, and salsa, or meat alone.
ALSO, they start off speaking to Edward Duran, the owner of Taqueria La Cumbre, and granted he's not the only one to lay claim to "inventing" the Mission burrito, but he retells the story about how Michaela Duran, back in 1967, wanted to make a big burrito that provided working people with enough food to get through a whole day, and enforcing the idea that La Cumbre made the first Mission-style burritos.
But I had always heard that Mission burrito dated further back than that, in particular to El Faro at Folsom and 20th. As their legend has it, the owner there, Febronio Ontiveros, made the first, large-sized burrito for a group of firefighters in 1961, using two six-inch flour tortillas because the giant Mission-style tortillas didn't even exist yet. Mexican food historian Gustavo Arellano has supported El Faro's claim to the Mission burrito and in Arellano's version, which is in his 2012 book Taco USA: How Mexican Food Conquered America, Ontiveros already had the large-sized tortillas because he'd known these kind of burritos from work camps when he first immigrated here, and those tortillas were available at that time in Sonora and Southern Arizona.
The SFGov video does also tell the El Faro story, but they present both legends as equally possible, rather than making any claim to history, and rather than doing some proper research.
Plus, there have to be some SF old-timers around who can settle this. There were Mission burritos before 1967, right old-timers?!