STILL CRAZY: Zoobombers swarm Mayor Sam Adams in 2009.

AGAINST ALL ODDS, Zoobomb is 10.

Portland's arguably best-known and least-definable bike club has been hauling absurd varieties of bicycles up to the zoo's MAX stop and hurtling down Washington Park's steep hills every single Sunday night for the past 10 years. In a town where clubs, bands, and traditions come and go, Zoobomb has stuck around, and the group is marking its 10th anniversary with five days of festivities this week.

Over time, the group that started as a hilarious good time—and was alternately pinned as a public menace or annoying mob—has become a genuine public institution. In 2009, Mayor Sam Adams helped unveil a Regional Arts and Culture Council-funded art piece on SW 13th and Stark that serves as a tongue-in-cheek monument to Zoobomb, as well as a lending library of the kids bikes preferred for 'bombing the hill on Sundays.

"I am supportive of Zoobomb because they are well organized, they care about and require safety considerations, they self-police, and they've been very responsible," says Adams (who, somehow, has never made it out for a Sunday night hill bomb himself). "It's a great Portland institution. It's great fun."

Zoobomb's relationship with city authorities was tenuous in its early years. TriMet cracked down on the group in 2003, excluding riders from the MAX for not hanging their tiny bikes on proper bike hooks. Periodically, the Portland police would run stop-sign stings on the hill or clip the lock on the group's giant pile of bikes chained to a downtown rack and confiscate them. Now the bikes are legally part of the group's public art sculpture and city officials are more concerned about skateboarders than the Sunday night Zoobomb.

"It's wild. I love being on the police's good side and trying to be the best people we can be to earn that," says "Handsome" Dave Terry, the official "bike librarian" of the tiny-bike collection Zoobomb lends out to anyone who wants to join the weekly ride. He estimates more than 10,000 people have Zoobombed since 2002.

Terry first rode the hill on a mini-bike in the summer of 2002, after some acquaintances told him it would be a thrill.

"I was like, wait, let me get this straight. You and your friends go to a public park at night and ride little kids' bikes? I don't want to say what went through my head, but I was like, 'No thanks, guys, some other time.'"

But once Terry was talked into going along and speeding down the hill, he never looked back.

There are too many ridiculous stories about Zoobomb to fit in any article, but old-school ‘bomber Zach Archibald telling of the group’s summer 2002 beginning is a good one. While distributing the first flyers for Zoobomb on a Critical Mass ride, Archibald wound up getting tackled and arrested while wearing just boxers and Nikes. The police let him out of Central Precinct booking just after nightfall.

“I run to Rocco’s [Pizza, formerly on SW Oak] and I throw the flyers down on the counter. People gave me some clothes, we grabbed some bikes, and that was the first time a dozen people went Zoobombing. That was the genesis.”

The size of the weekly ride varies wildly depending on the weather, dwindling to a core group of a dozen or so in the winter while occasionally ballooning to hundreds in the summer.

"It was like an open-source bike club. This is your club, what do you want to do with it?" says Zach Archibald. "People got a lot of positivity out of it."