New Castle Northwest is located in central Lawrence County at 41°1′17″N 80°21′11″W (41.021338, -80.352919), on the northwestern side of the city of New Castle, the county seat. The CDP is in the southern part of Neshannock Township and is bordered to the southwest by Union Township. The southwestern border follows the Shenango River, a southward-flowing tributary of the Beaver River, part of the Ohio River watershed.
Zip Codes in New Castle Northwest, PA that we also serve: 16105