 However, in 1951 a third NPA, area code 417, was created for the southwest, including the cities of Branson, Joplin, and Springfield.By late 1996 the proliferation of cell phones, especially in the Kansas City area, and other market reforms related to deregulation by the Telecommunications Act of 1996, required that northwestern Missouri received an additional area code.The supply of telephone numbers was further limited because the Kansas City LATA extends some distance into eastern Kansas, meaning that several numbers in area code 913, the area code for most of the Kansas side of the Kansas City area, were not available for use.