JOIN USIn New York and many other East Coast cities, it was a snowstorm that was making it difficult for demonstrators to stay camped out in public places.
The "Occupy" movement, which began six weeks ago in lower Manhattan to decry corporate influence in government and wealth inequality, has spread to cities large and small across the US and around the world.
Demonstrators have spent weeks camped out in parks, wearing the patience of city officials even those who have expressed some level of support for their cause.
In Portland, Oregon, police have allowed protesters to sleep in two parks surrounded by office buildings despite policies outlawing camping, but Mayor Sam Adams warned demonstrators last week that he would not allow them to take over any more parks.
Late Saturday, hundreds of protesters gathered in another park Jamison Square in the wealthy Pearl District and defied a midnight curfew.
About 30 people who had decided to risk arrest sat on the ground as other protesters walked around them and chanted "Whose Park? Our Park!" and "Make No Arrests."
When police moved in around 2 am, all but the sitting protesters backed off.
Police said the arrests were made on charges that included criminal trespassing, interfering with a police officer and disorderly conduct.