What you need to know about Bay to Breakers

The annual Bay to Breakers race is Sunday, meaning residents can expect a party atmosphere throughout the city but also some traffic woes.

Why it matters: There are few things as quintessentially San Francisco as the Bay to Breakers, the annual 12K known for its party vibes and epic costumes — or complete lack thereof.

Driving the news: The race begins by the bay on Howard and Main streets and goes west through the city to end at the "breakers" on the Great Highway.

• The start of the race is marked by people throwing tortillas — a tradition "nobody can really figure out where it came from," race director Kyle Meyers recently told KRON4 .

How it works: Participants — some dressed in costume, fully naked and/or part of a human centipede — run through Hayes Valley, up the notorious Hayes Street Hill , along the Panhandle and through Golden Gate Park.

Flashback: In 1912, the city hosted the first-ever Bay to Breakers, which was "an attempt to bring the city back together" after the devastating 1906 earthquake .

• At the time, the race went by the name of the "Cross City Race" and just 140 people participated, KQED reports .
• In 1964, following a change in sponsorship, the race was renamed "Bay to Breakers."

By the numbers: This year, Bay to Breakers expects about 20,000 registered participants, Meyers said.

• But many more are expected to join in, as there were about 30,000 unofficial participants last year to go along with the 17,000 registered, according to KQED.

What's next: Expect navigating throughout the city to be a challenge on Sunday due to street closures and rerouted Muni lunes.

• There will be traffic disruptions beginning Saturday at 7pm through Sunday at 4pm, according to the San Francisco Municipal Transportation Agency's site.
• Be sure to check out the full list of street closures here.