Lines on a map can separate languages, currencies, and laws. A border is the boundary that divides two countries or administrative regions. Some follow natural features such as rivers or mountain crests; others run in straight geometric lines drawn by treaty.

Borders control the movement of people and goods. Crossing points may be heavily fortified or nearly invisible. Disputed borders have sparked conflicts, while open borders facilitate trade and daily commuting. Modern borders are often monitored by technology as much as by physical barriers.

Cartographers must decide how to represent borders that are contested or poorly demarcated on the ground. The political reality of a border can change faster than the ink on maps. For residents living nearby, the line shapes daily life in concrete ways—from shopping trips to family visits.

• Line separating political territories
• May follow natural or artificial features
• Regulates movement of people and goods
• Can be peaceful or contested