Area code 309 covers west-central Illinois, including cities like Peoria, Bloomington, Moline, and Galesburg. It was established in 1957 after splitting from area code 815. This region is known for its manufacturing legacy, agricultural economy, and universities such as Illinois State University. Peoria, in particular, has been a cultural and industrial touchstone for the Midwest. Ten-digit dialing is not currently required. Area code 309 carries the character of Illinois' heartland, representing a blend of blue-collar industry, educational centers, and small-city Americana that defines the state’s interior.