The 312 Area Code (or Area Code 312) is located in the state of MO. Area Code 312 is one of the 269 3-digit telephone area codes in the USA. It covers roughly 1.63 million unique phone numbers and 5.08 million individuals near the city of Saint Louis
Area code 312 was put into service. In 1989 Area code 312 was split to form area code 708. In 1996 area code 312 was split again to form area code 773. In 2009 area code 312 was overlaid with area code 872.