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 .
Parol evidence rule
In a minority of U.S. states, (Florida, Colorado, and Wisconsin), the parol evidence rule is extremely strong and extrinsic evidence is always barred from being used to interpret a contract. This is called the Four Corners Rule, and it is traditional/old. In a Four Corners Rule jurisdiction, there are two basic rules. First, the court will never allow parol evidence if the parties intended a full and completely integrated agreement, and second, the court will only turn to parol evidence if the terms available are wholly ambiguous. The policy is to prevent lying, to protect against doubtful veracity, to enable parties to rely dearly on written contracts, and for judicial efficiency.