PHILADELPHIA (AP).- It was one of the worst acts of terrorism in U.S. history, a deadly deed that filled the New York City sky with smoke and debris, thrust the nation into war, prompted restrictive new laws and intensified hostility toward foreigners.

Yet it happened nearly a century before the Sept. 11 attacks, on Black Tom Island, a munitions depot in New York Harbor sabotaged by German agents and American collaborators in 1916.

This and other examples of domestic terrorism are part of a new exhibition at the National Constitution Center, tracing the evolution of revolution and exploring how panic and prejudice can disrupt the balance between safeguarding civil liberties and protecting the public.

"Spies, Traitors and Saboteurs: Fear and Freedom in America" opened Friday and runs through May 30. Created by the International Spy Museum in Washington, D.C., it examines acts of revolution, sabotage, protest, subversion and extremism by foreign-born and home-grown militants, activists and spies from the Revolutionary War to the post-9/11 present.

More than 80 domestic attacks from 1776 to the present are presented — and how they sparked government responses that have changed American life, from the 1918 Sedition Act to the creation of the Department of Homeland Security. It is left for visitors to reach their own conclusions about whether the various changes over time have been for the better, said Peter Earnest, director of the Spy Museum and a former CIA operative.

"These issues will be with us until the end of the republic," he said. The show was created to be a teaching tool for the young, a history refresher for the old, and a conversation starter for all, he said.

Interactive polling stations, developed with the Gallup Organization, ask visitors' opinions on the nation's response to events presented in the show — along with results of Gallup polls through history asking the same questions.

Among them: Should the government have the authority to deport people suspected of supporting hostile groups? Should the FBI be allowed to investigate groups opposed to the U.S. government? Is violence by individuals ever justified to bring about change in society?

"The exhibit illustrates in a way that's very dramatic and visceral the challenges we face as a country from threats that often originate internally," said David Eisner, National Constitution Center president and CEO. "How do we protect our homeland ... and how do we at the same time guarantee constitutional protections for all of our citizens?"

Included in the exhibit are a charred remnant of the White House torched by the British in 1814, Ku Klux Klan garments from the 1960s, and wreckage of the World Trade Center and the Alfred P. Murrah Federal Building in Oklahoma City. It also shows a replica of the bomb thrown during Chicago's deadly Haymarket riot in 1886, badges of American Protective League agents who spied on fellow Americans during World War I and a video interview with Bernardine Dohrn of 1960s radical group The Weather Underground. Some of the subject matter may be too intense for very young children.

Artifacts and documents illustrate how American collaborators helped German and Japanese agents execute domestic attacks preceding the world wars, reveal why the FBI compiled a dossier on Eleanor Roosevelt, and explain how the 1995 Oklahoma City bombing triggered a decline in so-called militia and patriot groups — until the Sept. 11 attacks.

The show also offers a reminder of the ways public hysteria can result in policies that suppress free speech and bolster racial and ethnic discrimination. Powerful examples include the "Red Scare" fervor and ensuing fallout after World Wars I and II, from targeting immigrants for mass arrest during the notorious 1919-1920 "Palmer Raids," to McCarthyism's attacks on intellectuals, artists and labor unions in the 1950s.

The exhibit will spark debate about the nation's current political tussles and how to learn from our past to make decisions that protect citizens from harm without destroying their individual rights, said James Doolin, an FBI agent who worked as a consultant on the exhibit with the National Constitution Center.

"We don't see it as a conflict, we see it as a balance," he said. "It's a balance we work on every day."



Copyright 2011 The Associated Press.