Area code 412 serves the state of Pennsylvania. This area code was assigned on January 1st, 1947. On January 1st, 1947 it went into service. 412 is a General Purpose Code. 412 service area does overlap with 878 area codes. Dialing pattern for local calls within the same NPA (area code) is 10D. All calls within and between NPAs 412 and 724 and 878 can be dialed as 10D or 1+10D. Calls to other NPAs must be dialed as 1+10D.