County Line Branch (also known as the County Line Branch of Chillisquaque Creek) is a tributary of West Branch Chillisquaque Creek in Northumberland County and Montour County, in Pennsylvania, in the United States. It is approximately 8.9 miles (14.3 km) long and flows through Lewis Township in Northumberland County and Anthony and Limestone Townships in Montour County. The stream's watershed has an area of 8.97 square miles.