Crews have been working day and night installing security fences around McCormick Place.
The coast guard cutter Holly Hock is now stationed along the lakefront while smaller boats control the Chicago River and closer to shore.
Military helicopters have been spotted flying over McCormick Place.
Demonstrators across the country are also arriving. A tour bus from New York City carrying members of the 99 Percent Solidarity Movement arrived Wednesday night in East Lakeview. More than a dozen more busses are expected to arrive from the West Coast and other East Coast cities Thursday.
"A peaceful protest is the primary goal," said one New York protestors. "There are always going to be fringe people who are going to act up and that is not the message that we're bringing here."
There were also protests in the Loop Wednesday. One rally at Federal Plaza called for the release of a Los Angeles activist and Occupy Chicago demonstrated along LaSalle Street against corporate greed and bank foreclosures.
Veterans of the Iraq War plan to hold a news conference Thursday morning to talk about why they are protesting NATO. They are going to take part in the big anti-NATO march and rally on Sunday when NATO convenes to give back their medals.
NATO opponents and NATO supporters face off in a debate Thursday night at the Pritzker Military Library. An Iraq war veteran and anti-war activist will argue against NATO while a former U.S. ambassador and a Loyola University political science professor will argue why the alliance is needed.