North American area code 513 serves southwest Ohio including Cincinnati and many surrounding cities, such as Forest Park, Hamilton, Lebanon, West Chester, Mason, Middletown, Norwood, Oxford, Harrison, Cleves, Miamitown and Trenton. It is one of the original area codes established in 1947, and originally covered the entire southwest quadrant of the state. In 1996, however, most of the northern and eastern portion of the old 513 territory, including Dayton, was split into area code 937.