Authorities stepped up patrols on Minnesota's northern border, law enforcement took to subways in New York and Boston, and more eyes watched theme parks in Florida and California after the latest terror alert warning on Friday.
Private businesses snapped to attention along with law enforcement. "If Secretary (Tom) Ridge says there's a reason to be more alert, we will be," said Dick Turner, general manager of the Embassy Suites Hotel in Chicago.
Some in government and business would not discuss what steps they took, if any, after the nation's terror threat level went from yellow to orange, the second-highest in the color-coded warning system.
"We have not eased up on any of our security measures since 9-11," said Gerard Hoeppner at Tampa's Busch Gardens. "We're aware, we're alert. The safety of our guests and employees is our highest priority."
Others said it was just one worry along with many others.
"I've heard the news," said Rob Huntley, general manager of The Inn At Union Square in San Francisco. "The likelihood of an earthquake is more of a huge concern of mine."
No specific targets were mentioned, though federal officials left little out, listing apartment buildings and hotels as potential targets along with facilities connected to transportation, energy and "symbols of American power."
As with past alerts, officials found themselves trying to warn people without panicking them.
"To be honest, going from yellow to orange for the average citizen means not much," said Massachusetts' Public Safety Secretary Ed Flynn. "Go on with your normal course of business."
Still, normal business could be thrown off as others in Flynn's state announced stepped-up patrols at Logan International Airport, on Boston's subways and in the waters off the Atlantic coast.
"What passengers may notice is increased state police patrols, more roadblocks and vehicle inspections," said Jose Juves, spokesman for the authority that runs the airport, where two of the planes in the Sept. 11 attacks were hijacked. "Passengers may see more frequent use of the bomb sniffing dogs also."
In New York, Gov. George Pataki said specialized units of the state police and the National Guard were activated. He and New York City Mayor Michael Bloomberg announced extra security at bridges, tunnels, airports, subways and many public buildings.
In addition, Pataki said the statewide alert was bumped to orange along with the nation. New York City has remained at orange level since Sept. 11.
After the federal government alerted state governments to the change, a network of contacts quickly spread the word, urban to rural, government to business, and on to the public.
"An alert government with alert citizens can really work together," said Jeff Luther, Minnesota's homeland security coordinator. "If they see something that seems suspicious, chances are it's suspicious. They should call the police department."
Luther said already-stretched sheriff's departments along his state's northern border with Canada would increase patrols, and would also rely on local farmers to be more alert.
Power companies were among those that responded.
"Although I can't tell you specifically, we have taken additional measures as a result of this declaration," said Steve Conroy of Southern California Edison, where security was increased at the San Onofre nuclear facility.
The FBI was in contact with National Grid, the company that owns Massachusetts Electric and energy providers in New York, New Hampshire, and Rhode Island. "We've asked employees to be extra vigilant," spokeswoman Jackie Barry said.
Out on the streets, though, things didn't look very different.
Janis Brakovskis, 32, a Latvian medical student on a fellowship in Connecticut, said he was led to believe that terrorist threats were much more imminent in America before he got here.
"Watching television and reading newspapers, it sounds like America's overrun with terrorists," said Brakovskis, who was visiting Boston on Friday. "But when I get here and look around, it seems perfectly safe."