The Research Triangle, commonly referred to as "The Triangle", is a metropolitan area/region in the Piedmont of North Carolina in the United States, anchored by the cities of Raleigh and Durham, and the town of Chapel Hill. Another popular term for this area is Raleigh-Durham, which is derived from Raleigh-Durham International Airport, which takes its name from the area's two largest cities. Its estimated total population as of 2005 was 1,509,560. The research universities of Duke University, the University of North Carolina at Chapel Hill, and North Carolina State University are located in this region. The "Triangle" name was cemented in the public consciousness in the 1950s with the creation of Research Triangle Park, home to numerous high-tech companies and enterprises. Although the name is commonly used to refer to the cities, "The Triangle" originally referred to the universities, whose research facilities and the educated workforce they provide are the major attraction for businesses located in the Park. The Triangle's population is the most educated in the United States, with the highest number of Ph.D.s per capita.^[1] The region is not be confused with "The Triad", which is the region directly west of the Triangle. Most of the Triangle is represented by, and closely associated with, the second and fourth congressional districts.

Source: Wikipedia, http://en.wikipedia.org/wiki/Raleigh-Durham