Ohio currently utilizes 12 area codes. When first established by AT&T and the Bell System in 1947, 216 covered northeastern Ohio including Cleveland, 419 covered northwest Ohio including Toledo, 513 covered southwest Ohio including Cincinnati, and 614 covered southeast Ohio including Columbus. The most recently added was 380 in 2016 as an overlay to 614. Today, 330 is the most populated with an estimated 2 million of the state's 11.5 million residents.
Sources: North American Numbering Plan Administration (NANPA), telecom providers, and the U.S. Census Bureau.