How long are the two U.S. borders? July 14, 2020September 13, 2011 by Pamela Landy The length of the Canadian border is 3,987 miles. The length of the Mexican border is 1,933 miles. Related Answers How long have people of Mexican descent lived in Los Angeles? Why are Oklahomans called Sooners? What is the largest rodent in the world? What was the “Mexican cession”? What action by Pancho Villa spurred the U.S. to invade Mexico in 1916? How big is Manhattan Island?