Updated

Just south of the U.S.-Canadian border in the Vermont town of Richford is a giant outpost, an imposing symbol of the changes wrought by the 9/11 attacks on the United States.

Built by the Border Patrol on 35 acres of land, the 26,000-square-foot structure is the base of operations for agents patrolling about a 25-mile stretch of the international boundary between Vermont and Quebec. It has state-of-the-art communications, a kennel for law enforcement dogs, a booking area with holding cells and office space for up to 50 agents. Outside there's a helicopter pad.

"This building is perfect, it meets all our needs," said Sean McVey, the agent in charge of the Richford station, who has worked in Vermont since 2004. "This gives us basically all the tools we need to do the job."

The enhanced security along the boundary that has been described as the longest undefended border in the world is probably the most visible change since 9/11 in northern Vermont, New Hampshire and upstate New York. Surveillance from helicopters and airplanes bolsters the border protection on the ground.

On 9/11 there were about 300 Border Patrol agents on the 3,987-mile northern frontier; crossing between the two countries was so casual some people didn't even carry identification.

In the immediate aftermath of the 9/11 attacks it was feared that some of the attackers had entered the U.S. from Canada, a fear that proved to be unfounded.

But security officials recognized that Canada's immigration policies enabled some people to enter that country from other parts of the world who would not be able to enter the U.S. directly or legally. The three states' shared border with Canada had dozens of back roads that crossed away from official ports of entry, potential routes into the U.S., it was feared, for other terrorists.

Within days of the attacks, National Guard soldiers were helping staff border posts. Plans were begun to triple the size of the Border Patrol and provide human and technological resources to the agents and border crossing staffers whose agency is now known as Customs and Border Protection, all part of the Department of Homeland Security. The facility was completed almost two years ago.

Now, a decade later the soldiers are back in their barracks and the process is nearly complete. While the Border Patrol won't provide precise figures, officials agree that the number of agents has about tripled and the technological enhancements are helping agents do their jobs.

The changes in Richford are typical. Since shortly after the Border Patrol was created in 1926 until the attacks, about three agents patrolled the area around Richford, based out of an office in the post office.

A photo in the entryway of the new station shows 14 uniformed agents now. Officials won't say how many are based at the new outpost, but hint there are more than when the picture was taken.

The U.S. now has what is, in effect, a border air force that patrols the region. Customs and Border Protection's office of Air and Marine flies both helicopters and airplanes from Plattsburgh, N.Y., just south of the border.

"We live in a sort of a desolate part of the country," said James Diskin, deputy director of air operations for CBP's Plattsburgh Air Branch. "When you get out into Vermont and New Hampshire, it allows us to do whatever we need to do, to get there as fast as we can to help out."

In addition to border patrols, the aircraft are available to help state and local law enforcement and emergency responders deal with other emergencies. Among the benefits are border reports of suspected drunken drivers trying to enter the U.S. The Border Patrol regularly backs up state law enforcement officers on local emergency calls; officials said the federal agents can reach a crime scene well before state police, in many cases in northern Vermont.

Another benefit post-9/11 is that federal, state and local law enforcement agencies now work much closer together than before the attacks, officials say.

That was evident in 1997 in the North Country town of Colebrook, N.H., when Carl Drega killed two state troopers, a judge and a newspaper editor, then disappeared. Law enforcement officers from four state and federal agencies had to park cruisers side-by-side so officers could retransmit radio broadcasts to make sure everyone knew what was going on. Drega was later killed in a shootout with police on a Vermont back road.

The agency was also involved in July when 11-year-old Celina Cass disappeared in Stewartstown, N.H. A CBP helicopter was used to help search for her shortly after she was reported missing and dozens of federal agents joined before the girl was later found dead. The circumstances of her death have not been determined.

Even before 9/11, efforts were made to improve law enforcement communications along the border. The process accelerated after the attacks.

"We did a pretty good job with the resources we had," said John Pfeifer, head of the Border Patrol's Swanton Sector, who was critically wounded in the Drega shootout. Pfeifer oversaw his agency's efforts in the search for Celina. "There was effort back then, but today there is a much more timely response and a greater response. It's kind of a neat parallel."