( CNN ) -- Eleven members of Greenpeace pleaded not guilty to federal charges after they were arrested for hanging a banner on South Dakota 's Mount Rushmore Wednesday to protest global warming as the G-8 summit in Italy begins . Greenpeace says it does not think its 2,275-square-foot sign will damage Mount Rushmore 's structure . `` America honors leaders not politicians : stop global warming , '' reads the 2,275-square-foot sign . Twelve protesters were arrested , but one was released after questioning . The others appeared before a federal magistrate Wednesday afternoon and received citations for illegal climbing and trespassing , according to federal prosecutors . Each person faces a maximum of six months in prison and possibly up to a $ 5,000 fine . The charged protesters came from eight states , including California and New York . The banner was up for an hour before it was seized . The National Park Service is holding it as evidence , authorities said . Watch tourists react to the protest » . Some of the demonstrators breached a controlled area and got to the top of the monument , Mount Rushmore spokeswoman Patty Rooney told CNN . Greenpeace , a nonprofit organization that supports environmental causes , said the sign is part of a global day of action to urge world leaders at the G-8 summit to make global warming a priority and to take the actions necessary to stop climate change . `` We are at a key moment in history when we must challenge our president to take real leadership , '' said Carroll Muffet , deputy campaign director for Greenpeace . `` The steps taken so far have been frankly inadequate . If President Obama wants to take his place among the great leaders of history , he must take aggressive measures to combat climate change and prioritize a strong deal in Copenhagen , '' Muffet said in a statement . `` We 're here at Mount Rushmore to inspire Americans to take action , and remind the world that heroism and leadership are part of our nation 's history -- and must be a part of our future , '' Muffet said . Watch how sense of urgency over climate change has dissipated at the G-8 summit » . The G-8 meeting , which includes leaders from the world 's most industrialized nations , is taking place in L'Aquila , Italy . Rooney said the monument will be assessed for any structural damage . She said a security system alerted park staff to the protest at midday . Greenpeace acknowledged the protest is illegal and dangerous , but said it does not believe the sign damaged the solid granite structure . The Mount Rushmore National Memorial features a carving of former U.S. presidents George Washington , Thomas Jefferson , Theodore Roosevelt and Abraham Lincoln . Nearly 3 million people visit the site every year . CNN 's Susan Candiotti and Ross Levitt contributed to this report .
NEW : 11 get citations for illegal climbing , trespassing for sign on Mount Rushmore . Greenpeace : Sign meant to urge G-8 summit attendees to address climate change . Comment: Protesters breached controlled area , reached top of monument , spokeswoman says .