The U.S.-Canada border crossing near Jackman, Me., and Armstrong, Que., Sept.12, 2001. (Jacques Boissinot/Canadian Press)

Washington had already taken significant steps to try to bolster border security before President George W. Bush announced plans on May 15, 2006, to send 6,000 National Guard troops to the border with Mexico. Along with the soldiers, Bush ordered new fences, cameras and unmanned aerial vehicles to stem the flood of illegal immigrants.

"The border should be open to trade and lawful immigration and shut to illegal immigrants as well as criminals, drug dealers and terrorists," Bush said in a nationally televised speech.

He didn't mention the Canadian border. But there have been suggestions that governors of some of the states that share the border with Canada might ask for similar measures.

The world's longest undefended land border has been attracting a lot of attention since the Sept. 11, 2001, attacks on the United States. Canada and the U.S. have taken steps designed to keep closer tabs on who and what crosses the border, while avoiding – as much as possible – complicating life for people and businesses that have grown used to travelling quickly and easily between the two countries.

Canadians have never had to go through the process of applying for a visa to visit the United States. Crossing was as simple as answering a few questions and showing your birth certificate – no photo required.

While there has been no talk of forcing Canadian families to get visas before spending some quality time with some of Walt Disney's most famous characters, the rules on what kind of documentation you will have to show are changing.

By Jan. 23, 2007, Canadians who are flying into the United States will have to use their passports. The U.S. estimates that 90 per cent of people flying in from Canada already show the passports. At land border crossings, Canadians will have to start using passports or a special ID card by June 2009.

Americans face the same rules. If they travel to Canada, they will be required to show secure ID on their return to the United States — either a passport or the ID card that's still to be designed.

The plan has caused concern on this side of the border.

In a speech to a New York audience, Canada's ambassador to the United States, Michael Wilson, called on the United States to look carefully at the potential economic consequences of the passport initiative. He warned the law could cause a "cooling effect" on cross-border travel and commerce.

The Conference Board of Canada has examined the issue and found that just nine per cent of Americans without passports would be interested in obtaining the new security card. The economic think tank predicts trouble ahead, especially for the tourism industry.

The U.S. Department of Homeland Security notes that only 20 per cent of Americans currently hold passports, compared to 50 per cent of Canadians.

The United States announced in October 2006 that it would develop a wallet-sized ID card for Americans to use instead of a passport. They will use radio-frequency identification technology that will link the cards to databases. Canada still hasn't decided whether it will follow suit.

Measures adopted since September 2002 have helped speed up cross-border traffic. Former prime minister Jean Chrétien and Bush met on the Ambassador Bridge between Windsor and Detroit that month to kick off two programs designed to ease movement through the busiest border crossings.

Both programs — NEXUS and FAST — are part of the Smart Border Declaration. NEXUS is a joint program of the American and Canadian customs and immigration agencies and provides a "fast lane" for frequent travellers across the border.

For $80, the government will issue an identification card to "pre-approved, low-risk" travellers. These travellers can use dedicated lanes to cross the border and are subject to little or no questioning or inspection from customs officials.

People who apply for a NEXUS card undergo an electronic scan of their index fingers for comparison against a database of immigration violators at the U.S. Immigration and Naturalization Service.

The FAST program involves registering importers, cargo carriers and drivers with the government before they reach the border. Carriers of low-risk cargo can be pre-approved to prevent long delays at border crossings.

Under FAST, an acronym for Free And Secure Trade, customs officials can be notified of the cargo's arrival up to an hour before it gets to the border. The pre-approved carriers and drivers use a dedicated lane to cross between the two countries.

In April 2006, Statistics Canada released figures showing that same-day trips by Americans to Canada had fallen significantly. While Statistics Canada didn't provide reasons for the drop, the Tourism Industry Association of P.E.I. points to a study it commissioned suggesting that 32 per cent of Americans already believe a passport is required at the border. The association said that's having an impact on border crossings.