The United States and Canada share the longest international border in the world, with its 5,525 miles stretching from Maine to Alaska. People have traveled across it for centuries. British loyalists--and Indigenous people who fought alongside them--fled to Canada after the American Revolution, as did enslaved individuals, who followed the Underground Railroad to seek liberty and safety. Bootleggers smuggled liquor into the U.S. during Prohibition, and by 1930, almost a million French Canadians had crossed the border to find work in New England mills. In addition, countless immigrants to the United States stopped in Canada first. Today, the 120 land ports of entry are busy, as those living in the U.S. and Canada regularly cross the border for work, to visit family, and to go on vacation.

A Brief History of the Border

The United States-Canada border, as it is known today, only dates to 1903. It formed as a result of centuries of colonization, war, revolution, and land acquisition through treaties with Indigenous peoples, as well as through diplomacy. If you had family who may have lived along these shared border areas during its early days (in the late 1700s, for example), understanding how the current borders came to be could give you some helpful context as you look into your family history.

French explorers were the first Europeans to settle permanently in Canada, and in 1608 Samuel de Champlain built a fort in what is now Quebec City. In the following decades, French claims expanded beyond the fort, while England established colonies farther south along the Atlantic Coast. France and England had long been rivals in Europe, and their disputes extended to North America as they struggled to control the North American continent. After Queen Anne's War (1702-13), Britain gained the territories of Nova Scotia, Newfoundland, and the Hudson Bay region. In 1763, after prevailing in the French and Indian War, called "La guerre de la Conquete" in French-speaking Canada, Britain gained nearly all French territory east of the Mississippi River. This event, however, also set the stage for Indigenous people to lose most of their lands, as the British sought new opportunities to expand settlements along the colonial frontier.

The American Revolution led to further bloodshed along the border, as the American colonists tried and failed to capture Quebec, Montreal, and Nova Scotia. When the Americans won the war, the Treaty of Paris established the border between the United States and British North America, although in doing so it ignored the treaties already in place with Indigenous communities along the boundary line. In the north of the newly established United States, the border was marked by the Great Lakes, the St. Lawrence River, and the 45th parallel--all the way east through Vermont. In Maine and New Hampshire, the squiggly line that separates the two countries follows rivers, lakes, and a meandering natural ridge.

As the U.S. and British Canada grew to the west, the two countries extended the border. It stretched along the 49th parallel, from Minnesota's Lake of the Woods in the east, to the Strait of Georgia, next to British Columbia in the west (which was roughly from Winnipeg, Manitoba, to Vancouver, British Columbia). Native nations on either side of the border were not consulted when this new boundary was established, leading to disruption, displacement, and even the destruction of their homes. The current land border between Canada and the lower 48 U.S. states has been in place since the Oregon Treaty of 1846.

Canada originally shared its western border with Russia, which had a colony in Alaska for 80 years. The two nations agreed on a boundary line in 1825 that roughly follows the Yukon River Valley and the 141st meridian. But after the United States purchased Alaska in 1867, it disputed the border on the southeastern coast. An international tribunal settled the matter in favor of the U.S. in 1903, awarding it the skinny stretch of coast known as the Alaska Panhandle. The Alaska portion of the U.S.-Canada border is 1,538 miles long.

Building Bridges to Help Cross-Border Movement

Despite all of the conflict surrounding the border, the U.S. and Canada have often worked together to build roads, bridges, and canals along it to streamline trade and the movement of people. In the 19th century, Britain was Canada's largest trading partner, but it still exported lumber, fish, and agricultural products to the U.S., and imported manufactured goods. If your ancestors lived in those border areas, could they have been involved in one of those building projects? Might they have worked to transport goods across the border?

The earliest cross-border infrastructure projects were in the east. Since 1848, the two countries have built multiple bridges near Niagara Falls. These include a railway bridge designed by John Roebling (the engineer of the Brooklyn Bridge) and the steel-arch Honeymoon Bridge, which collapsed after 40 years of heavy ice and high winds. The Rainbow Bridge opened in 1940 and still operates today; its name symbolizes the friendship between the U.S. and Canada. As Niagara Falls has long been a popular honeymoon destination, maybe some of your ancestors crossed one of those bridges during their visit.

The countries also jointly built the 5,160-foot Windsor and Detroit Tunnel in 1930 and the Thousand Islands Bridge in 1938.

U.S.-Canada Border Crossing Locations

Border crossing locations are often located next to lakes and rivers that span the two countries. Historically, these included St. Albans, Vermont, a major port of entry on Lake Champlain; Lewiston, New York, on the Niagara River; and Duluth, Minnesota, on Lake Superior. The iconic Peace Arch crossing sits between Seattle, Washington and Vancouver, British Columbia on the west coast. Many travelers also sailed into ports on the Atlantic and Pacific Oceans.

Large cities such as Buffalo, New York, have also been popular for border crossings via the Peace Bridge, but you could also enter Canada from the U.S. via small, landlocked towns like Noyes, Minnesota. Today, the busiest location is between Windsor, Ontario, and Detroit, Michigan, on the Ambassador Bridge, where typically 40,000 people cross each day.

Evolving U.S.-Canada Border Crossing Requirements

How people cross the border--whether for trade, tourism, or immigration--has changed over time. In the early 1900s, people would have traveled by foot, ship, or train. Now, they are more likely to enter by car or airplane, though it's still possible to walk (or bike) across the border.

For most of the 19th century, people could move freely across the border. The U.S. had very few immigration inspectors along its northern boundary until 1895, so Americans and foreign nationals alike could walk right in. The U.S. had stronger border protection at its ports, like Ellis Island in New York, and emigrants wishing to avoid inspection may have come into the country through Canada. Steamships even promoted the Canadian route as a hassle-free way to get to the U.S. The government finally caught on, and in 1895 it began placing border services officers along the boundary with Canada. It also worked with Canadian railroad and steamship companies to make sure passengers bound for the United States complied with U.S. immigration law.

Questions Inspectors Asked at Border Crossings: Insights for Family Historians

After 1895, when a ship arrived in Quebec, Halifax, Victoria, or another Canadian port, immigration officers inspected passengers bound for the U.S. They often asked foreign nationals detailed questions, including their age, marital status, occupation, citizenship, final destination in the U.S., and if they were going to join a relative. Some asked if a person had a health condition or mental illness--or even if they were a polygamist.

People who made land border crossings had sometimes lived in Canada for many years. Before 1906, records only exist for foreign nationals who crossed the border, not people born in Canada. That country had long been a destination for immigrants, especially from England, Scotland, and Ireland, so while those immigrants could appear in the early records as foreign nationals, their Canadian-born children might not. After 1906, all immigrants appeared in the US border crossing records regardless of birthplace.

How to Learn About Family Members Who Crossed the U.S.-Canada Border

Did a branch of your family live in Canada before moving to the United States? Might a family member's occupation have caused them to cross regularly between the two countries? And where might people from your family tree have crossed the border by boat, train, or plane? Ancestry(R) can help you find stories about your family from both sides of the border.

The Ancestry(R) card catalog contains extensive records related to border crossings, so remember to narrow your search using filters like nationality or birthplace, or by browsing a specific database. If your ancestors crossed back and forth between Quebec and the U.S., you may also find records in French.

Search records of border crossings into the U.S. The database Border Crossings from Canada to the U.S. includes information from 1895-1960 and has records for dozens of ports of entry from Maine to Washington State. The information varies, but it generally includes a person's nationality, birthplace, birthdate, and the names of their closest relatives in their home country and at their U.S. destination. Some even include a photograph. The dataset for Detroit, Michigan, Border Crossings (1905-1963) is one of the largest Ancestry(R) location-specific collections in this topic category (for the United States), containing more than 1.7 million records.

Explore Canadian immigration records. In 1908, the Government of Canada began recording the names of immigrants who crossed the border from the U.S. These border crossing records only go until 1935, but they can be quite detailed, covering a person's language, religion, and purpose in coming to Canada.

Check passenger and crew lists. Canada's incoming passenger lists recorded everyone on board ships arriving in major ports from 1865-1935. These records can include whether your relatives could read or write, where they embarked, and if they intended to become permanent residents of Canada. You can also find similar information on the passenger and crew lists for U.S.-bound vessels that arrived in Canada.

Browse lists of airline passengers. If your relatives were lucky enough to fly in the mid-20th century, they could also appear in airline passenger and crew lists. A database for planes landing in Washington State, for example, spans 1947-1957 and includes the date of arrival and previous residence.

Explore Your Family's Border Crossing Story

Find out if your ancestors sought to establish new roots on one side of the border or whether they crossed back and forth. Discover family stories from the U.S., Canada, and beyond through immigration records on Ancestry today.

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