Implementation details of the new area code were announced in NANPA Planning Letter #375 in March 2008. Permissive ten-digit local dialing of numbers in the existing 304 area code began no later than July 26, 2008. During this period, local 304 calls could still be dialed with just seven digits.
The implementation of the new area code, as detailed in NANPA Planning Letter #375, involved a transition from seven to ten-digit local dialing for numbers within the existing 304 area code. This transition began on July 26, 2008.