Hundreds of anti-Wall Street protestors blocked gates at some of the West Coast’s busiest ports in the U.S. and Canada, as part of a nearly three-month-old movement against what they say is corporate greed.

Monday’s protests caused a partial shut down of operations at some of the terminals in Oakland, California, and Portland, Oregon.

In Portland, hundreds of protesters blocked entrances at two terminals preventing trucks from entering. Employees of the terminals were told to stay home from work. In Oakland, unions representing dock workers and longshoremen sent workers home after hundreds of protesters blocked an entrance to the port. An International Longshore workers union official said 150 of the 200 workers were sent home. No workers were asked to work Monday night. Typically the night shift employs as many as 200 workers.

Similar demonstrations took place in Anchorage , Los Angeles , San Diego , and Seattle , as well as in the Canadian city of Vancouver.

Port of San Diego officials said the protest caused minimal disruptions to business, but did result in four Occupy protestors being arrested.

The demonstrations are called “Wall Street on the Waterfront” and are targeting SSA Marine, a shipping company that is partially owned by investment bank Goldman Sachs. Protesters accuse the company of unfair labor practices and union busting.

Goldman Sachs has been a regular target of the anti-Wall Street campaign.

The Occupy Wall Street movement began in New York in September. It says it represents the “99 percent” — those outside the top 1 percent of wealth holders.

Last week, Occupy protesters in Washington joined thousands of people, including jobless and underemployed Americans, for three days of demonstrations to press an agenda of jobs and economic equality.