Where in North America is area code 507?

Iowa:Area code 515 serves Des Moines, Iowa, plus Ames, Fort Dodge, Jefferson, Algona, Indianola and other areas in north central Iowa. Iowa was originally divided into three area codes, running vertically the length of the state. The 515 area code covered the whole central third of the state. In the year 2000 area code 641 was split off of 515. Today the 515 area code covers only about 30% of its original area, including the city of Des Moines and the areas northwest of there.