And by then, solidarity protests had popped up in San Francisco, Denver, Los Angeles, Boston and Chicago, among other cities.

The relative calm of the protests began to shatter in October, when hundreds were arrested on the Brooklyn Bridge as part of Occupy Wall Street.

Also in October, the site in Oakland became violent when police used tear gas after protesters reportedly threw paint and other objects at officers. Major clashes between police and protesters have taken place in Oakland since that event, and hundreds of people have been arrested.

Critics questioned whether those skirmishes would derail Occupy, and whether protesters would be willing to remain outside in the winter. But Occupy sites in many cities remain active -- perhaps helped by unseasonably warm weather.

-- CNN's Poppy Harlow and Paul Courson, CNNMoney's Julianne Pepitone, and CNN International's Maggie Lake and Ivan Watson contributed to this report.