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List of river borders of U.S. states facts for kids

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Many of the borders between U.S. states were created by people, often as straight lines. This is especially true in the West. But in other parts of the country, like the Midwest, Northeast, and South, many state borders follow rivers. In fact, only four states on the mainland (Colorado, Montana, Utah, and Wyoming) don't have any borders defined by rivers or waterways. Hawaii's borders are simply its islands.

US States Riverine Borders
Map of U.S. river/waterway state borders (highlighted)

How River Borders Are Decided

Usually, when a river forms a border, the line is in the middle of the river's main channel. This is called the "thread of the channel" or thalweg. It's a rule the United States got from England.

However, there are at least six special cases where the border is not in the middle of the river, but along one of its banks:

New Hampshire and Vermont

The border between New Hampshire and Vermont is the western bank of the Connecticut River. This means the entire river belongs to New Hampshire. This rule was set a long time ago by King Charles II in 1664. Even though Vermont tried to change it later, the United States Supreme Court said in 1933 that the border would stay on the west bank.

Kentucky and Nearby States

The borders between Kentucky and the states to its north – Ohio, Indiana, and Illinois – are based on the northern bank of the Ohio River. This means the entire Ohio River along these states belongs to Kentucky. This was decided after Britain won the French and Indian War in 1763. The river was then part of Virginia (and later Kentucky). In 1980, the U.S. Supreme Court ruled that the border is the low-water mark of the Ohio River's north shore as it was in 1792, when Kentucky became a state. Because the river has changed over time, the exact border in some places was agreed upon by the states in the 1990s.

Delaware and New Jersey

The border between Delaware and New Jersey along the Delaware River is a bit tricky. North of a certain point (39° 30' north latitude), the border is the eastern bank of the river. South of that point, the border is the western bank. This means parts of the river belong entirely to one state or the other, depending on the location.

Maryland and Virginia

The border between Maryland and Virginia is the southern bank of the Potomac River. This means the entire Potomac River along this border belongs to Maryland. This also applies to the border between Maryland and West Virginia, and between Virginia and Washington, D.C., because these areas were once part of Virginia or Maryland.

Alabama and Georgia

The border between Alabama and Georgia, south of West Point, Georgia, is the western bank of the Chattahoochee River at the average water level. This was decided by the Supreme Court in 1860.

List of River Borders in the U.S.

Many rivers form borders between U.S. states. Here are some of them:

The Charles River helped define part of the border between Massachusetts and Rhode Island. The Merrimack River also helps define part of the border between Massachusetts and New Hampshire, even though the border runs parallel to the river, three miles north of it.

U.S. States with River Borders

Almost every U.S. state has at least one border that follows a river or waterway. There are 44 states in total with river borders:

See also

Kids robot.svg In Spanish: Anexo:Ríos fronterizos interestatales de los Estados Unidos para niños

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