Area code 615

Area codes 615 and 629 are area codes in Tennessee serving Nashville (Davidson County) and the 12 surrounding counties. 615 is the main area code, while 629 is an overlay covering the same area that began service in 2014. Besides Nashville, Murfreesboro, Franklin, Gallatin, Hendersonville, and Lebanon are other major cities in the 615/629 service territory.

When area codes were introduced in October 1947, Tennessee's only area code was 901. During 1954, in a flash-cut, most of the state east of the Tennessee River's western bend was assigned 615, while 901 was restricted to Memphis and the western third of the state. This configuration remained in place for over 41 years.

In September 1995, most of the eastern portion of 615—including Chattanooga, Knoxville, and the Tri-Cities—was assigned area code 423. As a result, the state's three area codes were roughly coextensive with the traditional Grand Divisions of Tennessee; 423 served almost all of East Tennessee, 615 served Middle Tennessee, and 901 served West Tennessee.

Although this was intended to be a long-term solution, within a year 615 was nearing exhaustion due to the rapid growth of the Nashville area, as well as the proliferation of cell phones and pagers. This forced yet another split in September 1997; the 615 area was reduced to its current size, while most of the western, southern, and eastern portions of the old 615 territory—including Clarksville, Cookeville, Columbia, and Tullahoma—was split off as area code 931, which now almost entirely surrounds 615. This made 615 largely coextensive with the inner ring of the Nashville metropolitan area.

...
Wikipedia