One reason, he theorized, is that local police agencies need funds from the federal government, and surveillance of supposed "terrorists" might be a good way to keep getting the money. No matter the reason, the news that the Bush administration keeps about 1 million names on a terrorist watch-list is disheartening, Obuszewski said, since so many people cannot possibly warrant inclusion.

In February 2006, the national ACLU and its affiliates filed multiple federal Freedom of Information requests seeking records of Pentagon surveillance of anti-war groups around the country. Using information from a secret Pentagon database, NBC News reported that a unit of the Department of Defense had been accumulating intelligence about domestic organizations and their protest activities as part of a mission to track "potential terrorist threats."

"It serves no security purpose to infiltrate peaceful groups," said Michael German, a former FBI agent who specialized in counter-terrorism and who joined the ACLU two years ago as policy counsel in its Washington legislative office. "It completely misuses law enforcement resources."

Since the Sept. 11, 2001, attacks, German said, the government has "actively encouraged" local police agencies to become intelligence gatherers and to compile information that does not necessarily have a connection to criminal activity.

Despite the fact that the Maryland infiltrators' reports consistently said the activists acted lawfully, agents continued to recommend that the spying continue. Reports of the surveillance were sent to at least seven federal, state and local law enforcement agencies, including the National Security Agency, the police departments of Baltimore, Baltimore County, Annapolis and Anne Arundel County, and the state General Services police.

The documents released yesterday show the kind of information they were trading. Among other things, Obuszewski and fellow activists arranged a meeting with then-Rep. Benjamin L. Cardin in 2005 in which they asked him to support a timetable for withdrawal from Iraq.

Susan Goering, executive director of the ACLU of Maryland, said she feared that the documents released so far "may be only the tip of the proverbial iceberg."

In a letter sent yesterday to Gov. Martin O'Malley, Goering wrote that the state police had "recorded extensive information about specific individuals and groups, including describing their political outlook, whether they were articulate, what political activities they are engaged in, and attended private planning meetings in a covert capacity."

The only potentially unlawful activity mentioned anywhere in the documents, she said, were two instances of nonviolent civil disobedience. In one, activists refused to leave a guard station during a protest at the National Security Agency after bringing cookies and drinks for the guards, and in the other, they hatched a plan to place photographs of soldiers who died in Iraq on the fence surrounding the White House.

"Maryland residents should feel free to join a peaceful protest without fear that their names will wind up in police files," Goering wrote. "They should feel free to engage in nonviolent dissent without fear of being branded as 'terrorists' or 'security threat groups' in shared law-enforcement databases."