Quadripoint
The Four Corners Monument is the only point in the United States where four states meet: Colorado, Utah, New Mexico, and Arizona meet at right angles. The United States first acquired the area now called Four Corners from Mexico after the Mexican–American War in 1848. In 1863 Congress created Arizona Territory from the western part of New Mexico Territory. The boundary was defined as a line running due south from the southwest corner of Colorado Territory, which had been created in 1861. By defining one boundary as starting at the corner of another Congress ensured the eventual creation of four states meeting at a point, regardless of the inevitable errors of boundary surveying. The monument is centered at .
Four Corners, Maryland
Four Corners began as a 19th century agricultural community located at the crossroads on the Bladensburg and Colesville Roads. The community remained rural until the post-World War I building boom in suburban Montgomery County. Beginning in the late 1930s, Four Corners saw the development of Northwood Park, Woodmoor, Indian Spring Village, Indian Spring Terrace, North Hills of Sligo Park, and Fairway. These subdivisions expanded between 1945 and 1955 even as new ones, such as Northwood and Franklin Knolls, were constructed. The single-family house subdivisions that soon surrounded Four Corners had winding streets that formed an irregular grid in between major roads. Four Corners was largely developed by the late 1950s.