This US town can only be reached by land through Canada

Point Roberts, Washington sits on a small peninsula that dips just far enough south of the 49th parallel to fall inside the United States, cut off from the rest of the country by water. When the US-Canada border was fixed at that latitude in 1846, no one adjusted for the peninsula's shape, leaving about 1,300 Americans reachable overland only by driving through British Columbia. Residents cross the border routinely for school runs and grocery shopping.

— Wikipedia contributors, Point Roberts, Washington — Oregon Treaty, 1846