What Is The Only State That Borders One Other State

WhatIs the Only State That Borders One Other State?
The United States is a patchwork of fifty distinct states, each with its own shape, size, and set of neighbors. While many states share borders with two, three, or even more counterparts, there is a unique case where a state touches only one other U.S. state. That state is Maine. In the following sections we will explore why Maine holds this distinction, how its geography and history shaped its solitary border, and what makes this fact both interesting and emblematic of the broader patterns of state boundaries in America.

Introduction: The Concept of State Borders

When we look at a map of the United States, the lines that separate states are not arbitrary; they often follow natural features such as rivers, mountain ranges, or latitude lines, and sometimes they result from historical compromises, treaties, or colonial charters. The number of neighboring states a given state has can influence everything from interstate commerce and cultural exchange to emergency management and political representation.

Most states are surrounded by several neighbors—think of Missouri, which touches eight states, or Tennessee, which borders eight as well. At the other extreme, a few states have very few land borders. Maine stands out because it shares a land boundary with just one other state: New Hampshire. All of its other sides are either coastline (the Atlantic Ocean) or an international border with Canada. This makes Maine the sole state in the contiguous United States that borders exactly one other state.

Why Maine Borders Only One Other State

Geographic Setting

Maine occupies the northeasternmost corner of the United States. Its shape is elongated, stretching roughly 320 miles from north to south and about 190 miles from east to west at its widest point. To the west and southwest, the state is bounded by the New Hampshire border, which follows a combination of natural landmarks (the Salmon Falls River, the Piscataqua River, and a series of straight‑line segments) and survey lines established in the 18th century.

To the north and east, Maine meets the Canadian provinces of Quebec and New Brunswick, respectively. The southern edge is a rugged coastline along the Gulf of Maine and the Atlantic Ocean, featuring numerous bays, islands, and peninsulas. Because the state’s western side is the only side that contacts another U.S. state, Maine’s total number of U.S. state neighbors is one.

Historical Factors

The solitary border can be traced back to colonial agreements and the aftermath of the American Revolution.

1. Colonial Charters – The original Massachusetts Bay Colony’s charter granted it lands that extended far into what is now Maine. When Massachusetts later separated from Maine (which remained part of Massachusetts until 1820), the boundary between the two was negotiated based on existing settlement patterns and natural features.

2. The Treaty of Paris (1783) – This treaty ended the Revolutionary War and established the western boundary of the United States at the Mississippi River. It also affirmed the northern boundary with British North America (later Canada) along the 45th parallel in the east and the St. Lawrence River watershed in the west. Maine’s northern border with Canada was thus set by international agreement, not by negotiations with another U.S. state.

3. The Missouri Compromise and Statehood (1820) – When Maine entered the Union as a free state under the Missouri Compromise, its borders were largely already defined. The only remaining adjustment needed was the western line with New Hampshire, which had been settled earlier by surveyors working for both Massachusetts and New Hampshire.

These historical layers meant that, by the time Maine achieved statehood, its western edge was the only side that required a demarcation with another American state. The other three sides were already determined by natural features (the Atlantic Ocean) or international treaties (the Canadian border).

Comparison with Other Low‑Border States

While Maine is unique in having exactly one U.S. state neighbor, a few other states come close:

Alaska and Hawaii are special cases because they are non‑contiguous; they do not share any land border with another U.S. state. Maine, however, is the only contiguous state with a single U.S. state neighbor. This distinction makes it a frequent answer in trivia and geography quizzes.

The Maine‑New Hampshire Border: Details and Quirks

The boundary between Maine and New Hampshire is not a simple straight line; it follows a mixture of natural and surveyed segments:

• Southern Segment – Begins at the Atlantic coast near the mouth of the Piscataqua River, following the river upstream to a point near Dover, New Hampshire.
• Central Segment – From there, the line runs north along the Salmon Falls River until it reaches the confluence with the Cocheco River.
• Northern Segment – After the river, the border proceeds via a series of straight‑line survey points that were established in the early 19th century, cutting through forests and hills until it reaches the Canada–U.S. border at the northwest corner of Maine.

Because of the river‑following portions, the border has a slightly sinuous shape, which can cause minor jurisdictional questions over water rights, fishing, and environmental management. Nonetheless, the line is well‑marked and respected by both states.

Cultural and Economic Implications of a Single Border

Having only one neighboring state influences Maine’s interstate relationships in several ways:

1. Limited Interstate Commerce Corridors – Most of Maine’s overland trade with the rest of the United States passes through New Hampshire, primarily via Interstate 95 and U.S. Route 1. This creates a logical chokepoint but also means that infrastructure investments in New Hampshire have a direct impact on Maine’s economy.

2. Shared Regional Identity – The two states cooperate closely on issues such as tourism (the “New England” brand), environmental protection of the shared watersheds, and emergency response. The **New England Interstate

...Water Pollution Control Commission and other regional compacts, streamlining policies that might otherwise require separate negotiations with multiple states.

3. Political Alignment and Advocacy – Maine’s congressional delegation and state government often coordinate closely with New Hampshire’s representatives on federal issues affecting northern New England, such as forestry, maritime industries, and broadband infrastructure. Their shared geographic challenges foster a unified voice in Washington, D.C., despite occasional political differences.

4. Transportation and Logistics – The reliance on a single land corridor makes Maine particularly sensitive to disruptions on I-95 through New Hampshire, whether from weather, construction, or accidents. This has prompted Maine to invest in alternative routes, such as enhancing rail freight and developing the Port of Portland, while also advocating for coordinated emergency planning with its neighbor.

5. Cultural Distinction – Within the New England region, Maine’s isolation reinforces a strong state identity. With no competing land borders to dilute its cultural influence, Maine’s traditions—from its coastal heritage to its independent political streak—are more concentrated and clearly defined compared to states that are geographically “squeezed” between multiple neighbors.

Conclusion

Maine’s status as the sole contiguous U.S. state bordering just one other state is more than a cartographic curiosity—it shapes the state’s economic strategies, regional partnerships, and self-perception. The precise, river-defined border with New Hampshire, while occasionally complex, has fostered a pragmatic interdependence that benefits both states. In a nation where most states are linked to several neighbors, Maine’s simplicity on the map belies a nuanced reality: its single border amplifies both its vulnerabilities and its strengths, making it a unique case study in how geography can direct the flow of commerce, policy, and culture. Ultimately, this singular connection underscores a broader truth about American geography: even the most straightforward lines can tell the most intricate stories.