The majority of the border between Canada and the United States runs along which parallel of latitude?

• A. 42 degrees
• B. 49 degrees
• C. 60 degrees
• D. 38 degrees

Answer: (B)

Lines of latitude run east-west, and a border that follows one sits at a fixed height north of the equator. The Canada–United States boundary uses a long stretch along the 49th parallel north. This line was set in the mid-1800s by the Oregon Treaty, which established the boundary along that latitude from the Rocky Mountains to the Pacific Ocean. Because of that treaty, most of the border between the two countries sits along 49 degrees north on maps. There are a few small deviations where the line follows waterways or local geography, but the vast majority runs along that latitude. The other numbers are much farther north or south than where the border actually lies.