A boundary is a real or imaginary line that separates two things. In geography, boundaries separate different regions of Earth.


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Geography, Human Geography, Physical Geography, Social Studies, World History

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A boundary is a real or imaginary line that separates two things. In geography, boundaries separate different regions of Earth. There are many different types of boundaries.

Physical Boundaries

Boundaries separate people and places. The most obvious type of boundary is a physical boundary. A physical boundary is a natural barrier between two areas. Rivers, mountain ranges, oceans, and deserts are examples. Many times, political boundaries between countries or states form along physical boundaries. For example, the boundary between France and Spain follows the peaks of the Pyrenees mountains.

Rivers are common boundaries between nations, states, and smaller political areas, such as counties. The United States' Mississippi River is the defining boundary between many of the states it winds through, including Arkansas and Tennessee, and Louisiana and Mississippi.

Another type of physical boundary lies below Earth's surface. Earth's shell, or crust, is made of thick slabs of rock called tectonic plates. There are seven major tectonic plates and many smaller ones. These plates are constantly moving.

Interaction between tectonic plates creates activity on their boundaries. Sometimes, the plates spread apart from each other, creating ocean trenches and, eventually, continents. When these plates move around, they can cause large cracks in the earth, called fault lines. Volcanoes and earthquakes are more likely to happen along fault lines.

The fault line between the Pacific and North American plates makes the U.S. state of California more likely to have earthquakes.

Political Boundaries

Political boundaries are the dividing lines between countries, states, provinces, counties, and cities. These lines, more often called borders, are created by people to separate areas governed by different groups. Sometimes, political boundaries follow physical boundaries. Most of the time you can't see them. Most maps show political boundaries.

Political boundaries change over time through wars, treaties and trade. After World War II, Germany's eastern border was moved farther west. The country itself was later divided into East Germany and West Germany.

In 1803, the United States bought a massive piece of land in a treaty with France. This land, called the Louisiana Purchase, expanded the size of the U.S. The western boundary of the U.S. moved from the Mississippi River to what is now Yellowstone National Park. The U.S. gained areas we now know as Missouri, North Dakota, South Dakota, Minnesota, New Mexico, Colorado, and many more.

An important type of political boundary in the United States is the boundary of a congressional district. This is an area that elects a representative to the U.S. House of Representatives. Its drawing depends on the findings of the U.S. Census, a population survey of the country taken every 10 years. If the population of a state grows or shrinks, that state may gain or lose a representative in the House. When this happens, congressional district lines are redrawn.

Other Boundaries

Political boundaries are just one type of artificial boundary. Other boundaries created by people include language, economic, and social boundaries.

Language boundaries form between areas where people speak different languages. Often, these boundaries match political boundaries. For example, the most common language in France is French.

In India, more than 100 different languages are spoken. The Indian government recognizes 22 of these as official languages. People who speak these languages are generally split into different regions. Not being able to speak a neighboring region's language can cause tensions between people.

Economic boundaries divide people with different levels of wealth. Sometimes these boundaries happen along borders between countries. The border between the wealthier country of the United States and the less-wealthy country of Mexico is both an economic boundary and a political one.

Sometimes, economic boundaries fall within a single country, and even within a single city. For example, Manhantan's Upper East Side, in New York, New York, U.S., is a wealthy neighborhood. It has famous colleges and hospitals. The Bronx's Melrose is a poorer neighborhood just a few kilometers (miles) away from the Upper East Side. Its residents struggle to access the excellent education and healthcare available just a couple kilometers away.

Natural resources also play a part in economic boundaries. Some people settle in areas rich in resources, like underground oil or fertile soil. These people are more likely to become wealthy, while people who live in areas without many resources stay poor. People are also willing to pay more to live in areas with access to better resources. This might be beautiful views, excellent schools, hospitals, or access to shopping.

Social boundaries occur where differences between groups' ways of life lead to unequal access to resources and jobs. Some of these boundary issues include race, gender, religion, and physical abilities. In some places, women may not have access to certain jobs or be allowed to travel in certain areas. Until 2019, in Saudi Arabia all women had to have a male guardian. This guardian's approval is required for women to travel, seek healthcare, manage personal finances, marry, or divorce. This social boundary discourages many women from seeking leadership positions in business or government.

People of different races may be forced to stay in different neighborhoods. Bahrain is a country in the Middle East. Many people from Southeast Asia have moved to Bahrain to find work. Political leaders have forced the country's Southeast Asian population to move to parts of the country where they will not live in communities with native Bahrainis.

Social boundaries can also form along religious lines. The nation of Sudan has many distinct religious social boundaries. Northern Sudan has people mostly following Islam, while southwestern Sudan is mostly Christian. Sudan suffered more than 20 years of civil war, and the people of southern Sudan voted to leave Sudan as a separate nation, called South Sudan, in 2011.

Language, economic, and social boundaries are not as sharply defined as political and natural boundaries.

Fast Fact

Maritime Boundary
A maritime boundary divides the ocean into areas controlled by different governments or no governments at all. The United Nations Convention on the Law of the Sea establishes a maritime boundary no more than 200 nautical miles (370 kilometers/230 miles) from a nation's coastline.

Fast Fact

Personal Boundary
Personal boundaries are the physical and emotional boundaries a person establishes around himself or herself. Different people have different boundaries: Some people reject most physical contact, such as a handshake, upon greeting. Other people embrace when they meet.

Fast Fact

Boundary Survey
A boundary survey establishes the exact property lines of a parcel of land. Boundary surveys are carried out by surveyors and engineers using historical records, field observations, and careful measurement.

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Hilary Costa
Erin Sprout
Santani Teng
Melissa McDaniel
Jeff Hunt
Diane Boudreau
Tara Ramroop
Kim Rutledge
Hilary Hall
Mary Crooks, National Geographic Society
Tim Gunther
Jeannie Evers, Emdash Editing, Emdash Editing
Kara West
Educator Reviewer
Nancy Wynne
National Geographic Society
Last Updated

October 19, 2023

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