One protester, Matt Sky, 27, told The New York Times the demonstration against corporate greed was necessary to show the movement's vibrancy.
"Everything about this movement is momentum," Sky said. "We need to show people that we are still relevant."
In Des Moines, Iowa, Occupy protesters established an around-the-clock presence outside President Barack Obama's re-election campaign offices. They hung a sign on the door reading "Obama's former headquarters."
"It started this morning when we came to air our grievances to the president and he locked us out," protester Frank Cordaro told The Des Moines Register. "We decided this is no time to give up this space.
"People are committed to staying 24/7, now we have to figure out how we can sustain it, support them and prepare for a course of reaction of the authorities if they should come and arrest us."
The newspaper said Obama campaign officials could not be reached for comment.
Some of the New York protesters used a ladder to scale a chain-link fence to gain access to Trinity Episcopal Church's property, while others lifted the fence from the bottom so others could scoot underneath it.
The protesters were joined by a few clerics, including Bishop George Packard.
Police quickly moved in to start making arrests.
The church's rector, the Rev. James H. Cooper, said while the church supports the protesters' call for social and economic justice, "We do not, however, believe that erecting a tent city at Duarte Square enhances their mission or ours."