 The largest city by population in the numbering plan area is the Kansas state capital, Topeka.When area codes were implemented in 1946, the southern half of the state (Dodge City, Emporia, Garden City, Wichita) was designated as numbering plan area 316, while the northern half (Kansas City, Topeka, Lawrence, Goodland, Manhattan, Salina, Hays) received area code 913.This configuration remained in place for 40 years.