The 791 area code is not currently used in North America. However, it is sometimes confused with the 719 area code, which is utilized by the Colorado Springs metropolitan area.
Area codes are designed to designate a specific area or geographic region. These codes are assigned to particular areas by the Federal Communications Commission (FCC). Depending on the number of residents in a particular area, some larger cities can have two or three different area codes assigned to them. With the advent of the cell phone and portable number porting, the use of area codes to determine a caller's exact location is dwindling.