A border is a physical or political line that separates geographic areas. Borders are used to delineate countries, states, provinces, counties, cities and towns. A border outlines the area that a particular governing body controls. The government of a region can only create and enforce laws within its borders.

Borders change over time. Sometimes the people in one region take over another area through violence, colonialism or imperialism. Following a war, land may be divided or borders may be redrawn as part of an international peace agreement. Other times, land is traded or sold without violence, though not always with the consent of the Indigenous people living there. For example, Russia sold Alaska to the United States, but the leaders of the Indigenous groups living there were not consulted, did not participate in the negotiations and were not paid for the land that was sold because they were not considered citizens of either country.

Sometimes, borders fall along natural boundaries, like rivers or mountain ranges. For example, the boundary between France and Spain follows the crest of the Pyrenees Mountains. For part of its length, the boundary between the United States and Mexico follows a river called the Rio Grande. The borders of four countries—Cameroon, Chad, Niger and Nigeria—divide Africa’s Lake Chad.

Some cultures use natural boundaries to divide up land. Native Hawaiians developed a land-sharing system called ahupua’a. This system cut up islands like slices of a pizza, with every border starting at a point in the middle—usually the top of a mountain or volcano—and extending down to the sea. The size of the ahupua’a depended on the amount of natural resources in the area. Areas with more condensed resources had smaller ahupua’a and areas with spread out resources made up larger ones. This gave different communities equal access to resources and the ocean.

Borders, particularly national borders, affect travel and migration. People can usually move freely within their own country’s borders but may not always be allowed to cross into a neighboring country.

Neighboring countries sometimes make agreements that allow their citizens to move freely between them. For example, 29 countries in Europe are part of the Schengen area, a zone where citizens may travel freely between the countries without being checked at the border. Of these 29 countries, 25 are part of the European Union (EU) and four are non-EU members.

On the opposite extreme, the Korean Demilitarized Zone—the border between communist North Korea and capitalist South Korea—is one of the most heavily militarized borders in the world. The zone, which is 4 kilometers (2.5 miles) wide and over 243 kilometers (151 miles) long, separates the two countries with barbed wire fences, land mines and armed guards. Though the border is dangerous for people, it has become a haven for plants and wildlife, particularly some endangered species, as the lack of human development has allowed the area to revert to its natural state. Under normal circumstances, foreigners can only visit North Korea through official tourism groups. North Koreans are not allowed to travel internationally without permission from the government.

The border between North and South Korea is also an example of how borders can divide people who share a common heritage. The Korean people have a shared history, culture and language, making the border between North Korea and South Korea purely a political one. Another example of a political boundary is the border that divided East and West Germany from 1949 to 1989. This border was formed at the end of World War II, when Germany was occupied and administered by the four Allied Powers: the United States, the United Kingdom, France and the Soviet Union. The territories controlled by the United States, the United Kingdom and France were combined to form West Germany (the Federal Republic of Germany). The area controlled by the Soviet Union became East Germany (the German Democratic Republic). This division created a clear political boundary between the two countries. In 1990, following the fall of communism in Eastern Europe, Germany was reunified, and the border was dissolved.

Every country has its own rules about who may travel, work and reside within its borders. Visas and work permits are government documents issued to non-citizens that limit the type of work or travel they may do in the country and for how long. The United States issues “green cards”—officially known as permanent resident cards—that allow non-Americans to live and work within the country’s borders.

Borders do more than just break people into different political zones. They are also used to divide, hold and maintain resources, giving access to those within the borders and denying access to outsiders. Borders also influence the distribution of resources, goods and services, which are often impacted by trade laws and tariffs. Borders can have ecological and political effects, as they build nations, reinforce power structures and establish that human-defined structure onto the natural world.

Borders also impact the psychological realm. They can be used to build the identity of those within the border, creating an “in group” and an “out group” and establishing divisions between them. While this can create a positive sense of belonging, it also can contribute to the isolation, ostracization and denial of rights to “outsiders.”

Border Protection

Many countries have some sort of military or law-enforcement presence along their borders. Countries protect their borders for several reasons. One is to keep out invaders. This is especially true in areas where two or more countries have fought over the same land for many years. Cambodia and Thailand, for example, have disputed the territory of the Preah Vihear Temple for more than a century. France, which had colonized Cambodia, created a map giving the entire territory to Cambodia in 1904. Thailand claims this map is inaccurate and rejects Cambodia’s right to the land. To this day, Cambodian and Thai military units are positioned along the border near the Preah Vihear Temple, and skirmishes often result in deaths on both sides.

Border Disputes

Many of today’s border disputes stem from the colonial era, when European colonizers created borders with little regard for the ethnic, political or historical experiences of the groups already living in the region. During the 1800s and 1900s, European countries created borders among African nations and divided up their control. These colonizers not only ignored the communities of Indigenous people already living there, they often purposely fueled division and conflict among Indigenous communities as a conscious effort to keep them from uniting and rising up against the colonizing nation. For example, Belgium purposely sowed conflict between the Hutu and Tutsi ethnic groups in what is now Rwanda by granting the smaller Tutsi community greater social and political privileges. In 1962, when Rwanda gained its independence, the Hutu majority took control. Fighting between the two groups came to a head in 1994 when the Hutu government engaged in a genocide that killed at least 500,000 Tutsis and moderate Hutus. The Tutsis fought back and took control of Rwanda, forcing millions of Hutus to flee into the nearby Democratic Republic of Congo and other neighboring countries. The ongoing war between the Hutus and Tutsis is just one of many similarly wrought conflicts on the continent of Africa. As Africans overthrew the colonizing countries, the divisions Europeans created or encouraged caused problems for the indigenous Africans trying to build a nation. Today, there are activists working to bridge some of the challenges created by these borders. For example, Emeka Okereke is a National Geographic Explorer who organized a team of artists to travel through Africa and examine the results of geopolitical borders along with local Indigenous people.

Again and again, borders drawn without reference to existing communities have been shown to create conflict and ongoing border disputes. People who have a border running through their community often reject the border in an effort to reunify their community. For example, the Kurds are an ethnic group that live across several countries, with a large population in Türkiye. Kurds, who also have their own language, began advocating for their own nation after World War I but were separated by borders created by European powers with the Treaty of Lausanne in 1923. Since then, Kurds have been fighting for their own separate nation. The People’s Democratic Party is mainly made up of Kurds who are advocating for their rights in Türkiye. Kurds continue to face discrimination by the Turkish government. One Kurdish nationalist group, the Kurdistan Workers’ Party, is considered a terrorist organization by Türkiye, the United States and a few other countries.

Borders are also disputed when countries vie for control of regions that are geographically advantageous. This can be because the disputed territory is in a good position for trade or military control. One example of this is in the Persian Gulf, where three small islands in the Strait of Hormuz between Iran and the United Arab Emirates (UAE) are disputed territories. When the UAE earned its independence from Britain, Iran seized the islands. The UAE claims ownership over the islands because they were supposed to be transferred from the British to the UAE when they were decolonized. These islands are important because oil is shipped through the Strait of Hormuz, and the nation that controls the islands has greater power over those shipments. It is also an important waterway for the militaries of several nations.

Many border disputes occur when people fight over natural resources. For instance, Sudan and Egypt have quarreled for decades over a region called Hala’ib. This triangle of land along the Red Sea is rich in the mineral manganese, which is essential to iron and steel production. It is also used as an additive in unleaded gasoline. The dispute originated during the colonial era, when British colonizers drew and redrew the boundary between the two nations. In 1899, the British created a political boundary between Egypt and Sudan, giving control of the area to Egypt. However, a few years later in 1902, they gave control of some of the area to Sudan so they could keep together and govern the indigenous tribes that lived there. Today, the Egyptian government recognizes the 1899 boundary giving them the Hala’ib. They claim that this is the political boundary, and the 1902 boundary was only administrative. Sudan recognizes the 1902 boundary.

Border controversies can extend to or be reflected or reinforced in cartography. The South China Sea is part of the Pacific Ocean between China, the Philippines, Vietnam and other countries, and it has many natural resources. China has claimed much of the South China Sea and, in the 2020s, increased its military presence there to increase its hold. The other nations reject their claim and accuse them of encroaching on their territory. Maps released by the Chinese government in 2023 showing the entire South China Sea as being part of China created an uproar, with Vietnam, Malaysia and the Philippines rejecting its validity.

Borders are not just lines on a map; rather, they are powerful tools that shape the human experience. They can encourage cooperation or cause conflict, protect rights or suppress them, and enhance ethnic and cultural history or erase it. As the world becomes more interconnected, questions about how borders are drawn, defended, and challenged continue to spark debate. Understanding how borders are formed and why they matter is essential to understanding the world today—and the forces that continue to shape it.