The protests marked an escalation from previous demonstrations as they went beyond boisterous rallies at park encampments and took aim at a major hub of commerce, such as the Port of Oakland. Organizers say they want to halt "the flow of capital" at the port.
The union representing port workers said it cannot ask members to participate in the protests because of clauses in its contract, potentially minimizing any disruptions.
Demonstrators as well as city and business leaders expressed optimism that the widely anticipated "general strike" would be a peaceful event for a city that became a rallying point last week after an Iraq War veteran was injured in clashes between protesters and police.
Embattled Oakland Mayor Jean Quan, who has been criticized for her handling of the protests, said in a statement that she supported the goals of the protest movement that began in New York City a month ago and spread to dozens of cities across the country.
"Police Chief (Howard) Jordan and I are dedicated to respecting the right of every demonstrator to peacefully assemble, but it is our duty to prioritize public safety," she said.
Protesters planned to hold rallies across the country in solidarity.
In Philadelphia, police arrested about a dozen protesters who were sitting peacefully inside the lobby of the headquarters of cable giant Comcast. Officers moved in after they refused to leave. The protesters were handcuffed and led into police vans as supporters cheered.
In New York, about 100 military veterans marched in uniform through Manhattan to protest what they called police brutality against the Iraq War veteran injured in Oakland.
Students from colleges in Boston and union workers, for example, were expected to march on local Bank of America offices, the Harvard Club and the statehouse to protest the nation's burgeoning student debt crisis.
They say total student debt in the country exceeds credit card debt, increases by $1 million every six minutes and will reach $1 trillion this year, potentially undermining the economy.
Along with protesting financial institutions that many within the movement blame for high unemployment and the foreclosure crisis, supporters of the Oakland events are expanding their message to include school closures, waning union benefits and cuts to social services.
Nurse, teacher and other worker unions are taking part in the protests, and Oakland is letting city workers use vacation or other paid time to take part in the general strike. About 5 percent of city workers took the day off Wednesday, according to City Administrator Deanna Santana.
About 360 Oakland teachers didn't show up for work, or roughly 18 percent of the district's 2,000 teachers, said Oakland Unified School District spokesman Troy Flint. The district has been able to get substitute teachers for most classrooms, and where that wasn't possible children were sent to other classrooms, he said.
The day's events in Oakland began with a rally outside City Hall that by midmorning drew more than 1,000 people who were spilling into the streets and disrupting the downtown commute.
About three dozen adults with toddlers and school-age children formed a "children's brigade, gathering at Oakland Public Library for a stroller march to the protest in downtown Oakland. Demonstrators handed out signs written as if in a children's crayon that read "Generation 99% Occupying Our Future," which the marchers attached to their baby backpacks and strollers.
The protests were expected to culminate with a march to the Port of Oakland, where organizers said the goal would be to stop work there for the 7 p.m. shift. Organizers say they want to halt "the flow of capital" at the port.
It is the only West coast port that exports more than it imports, according to port spokesman Issac Kos-Read. About 55 percent of the goods it handles are for export. Much of California's agricultural production flows through to foreign markets, including wines from Napa and Sonoma valleys, fruits and nuts from the Central Valley and rice from farms near Sacramento.
About 70 percent of the port's trade is with Asia. Seventeen percent is domestic and military cargo, 10 percent is European trade. The port imports electronics, apparel and manufacturing equipment, mostly from Asia. The port also handles imported cars and car parts from Asian carmakers such as Toyota, Honda, Nissan and Hyundai.
On Wednesday morning, the port was operating as normal and most longshoremen had shown up for work, according to port and union officials.
Craig Merrilees, spokesman for the International Longshore and Warehouse Union, said its members were not being called to strike. The union cannot sanction a strike in support of Occupy Oakland under the terms of its contract, he said.
"The general message is that the ILWU and other unions are supporting the concerns raised by Occupy Oakland and the Occupy movement to speak up for the 99 percent and against the corporate greed that is wrecking America," Merrilees said.
Other demonstrators, some affiliated with established community groups, said they planned to target banks, convene a dancing flash mob, sponsor music and street parties, march with elderly residents and people with disabilities to the California state office building, hold youth teach-ins.
Because of the activities' free-flowing and unpredictable nature, city leaders said they had no idea how many people would take part or how much a disruption they could pose to the daily routines of residents and workers.
City spokeswoman Karen Boyd said the government "will be open for business as usual" and was encouraging businesses to do the same.
The president of the police officers' union said he was worried officers were being scapegoated by Quan and "set to fail" if Wednesday's actions got unruly.
"We're going to be seen as the establishment, and it's not fair to the police, it's not fair to anyone," Oakland Police Officer's Association President Sgt. Dom Arotzarena said.
On Oct. 25, police acting at the request of the city's administrator, who reports to the mayor, were asked to clear the protesters' campsite during an early morning raid. A confrontation with marchers protesting the raid followed that night, and an Iraq War veteran suffered a fractured skull and brain injury when officers moved in with tear gas, flash grenades and beanbag projectiles.
Quan allowed protesters to reclaim the plaza outside City Hall the next day. At least six dozen tents and a kitchen buzzing with donated food have been erected on the spot since then, while the crackdown has galvanized anti-Wall Street events elsewhere and made politicians in other cities think again about interfering with their local encampments.
Occupy LA, a monthlong 475-tent encampment around Los Angeles City Hall, is planning a 5:30 p.m. march and rally through downtown LA's financial district to express solidarity with the Oakland general strike and to protest police brutality.
"It was obvious to the entire world that the acts perpetrated against Oakland occupation were acts of police brutality," said Julia Wallace, spokeswoman for the Committee to End Police Brutality at Occupy LA.
Unions representing city government workers, Oakland's public school teachers, community college instructors, and University of California, Berkeley teaching assistants all have endorsed the daylong work stoppage and encouraged their members to participate.
"It's sort of a realization that a lot of people are having that we've all been fighting our own issues, but really, it's all related, it's all the same issue," Oakland Education Association Secretary Steve Neat said.
The Oakland Metropolitan Chamber of Commerce said in a letter to the mayor Tuesday in which President Joseph Haraburda expressed concern for "the mothers and children, and even grandmothers, who plan to come to Oakland to conduct their regular business" and for business owners who "must face a day of uncertainty" if they do not close for the strike.
"We want to be clear, should Wednesday's planned protests go awry, someone will need to be held accountable," Haraburda said.
Associated Press writers Terry Collins in Oakland, Beth Duff-Brown in San Francisco, Mark Pratt in Boston, JoAnn Loviglio in Philadelphia, Jon Fahey and Verena Dobnik in New York and Christina Hoag in Los Angeles contributed to this report.