County Line Branch is a tributary of West Branch Chillisquaque Creek in Northumberland County and Montour County, in Pennsylvania, in the United States. It is approximately 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. Its tributaries include Beaver Run and McKee Run. The main rock formations in the watershed of County Line Branch are the Hamilton Group, the Onondaga and Old Port Formation, the Trimmers Rock Formation, and the Keyser and Tonoloway Formation. The soil series in the watershed include the Chenango-Pope-Holly series, the Berks-Weikert-Beddington series, the Hagerstown-Edom-Washington series, and the Watson-Berks-Alvira series. Industries in the watershed include agriculture and timbering. The Mountour County Natural Heritage Inventory lists the headwaters of County Line Branch as a "locally significant" site.
Course
County Line Branch begins near the border between Anthony Township, Montour County and Lewis Township, Northumberland County, near the northern borders of both townships. The headwaters are in the Muncy Hills. The stream flows south for several miles with few turns, following the Northumberland/Montour County line. Eventually it makes a sharp turn southeast and leaves the county line. Upon leaving the county line, the stream begins flowing roughly parallel to the border between Anthony Township and Limestone Township, Montour County. During this stretch, the stream crosses Pennsylvania Route 44 and Pennsylvania Route 54 and at the southern edge of the stretch, it receives the tributary Beaver Run. It then turns northeast into Anthony Township, where it picks up the tributary McKee Run. The stream then turns southeast and reaches its confluence with West BranchChillisquaque Creek at the southern edge of Anthony Township. County Line Branch joins West Branch Chillisquaque Creek upstream of its mouth.
Tributaries
Tributaries of County Line Branch include Beaver Run and McKee Run. The stream also has unnamed tributaries.
Hydrology
The entirety of County Line Branch and the entirety of each of its tributaries is considered by the Pennsylvania Department of Environmental Protection to be impaired. The stream and a number of its tributaries are affected by siltation due to agriculture.
Geography and geology
County Line Branch has an elevation of at its mouth. Much of the southern part of the watershed of County Line Branch lies over rock of the Onondaga and Old Port Formation. Some of the southern part of the watershed, however, is over rock of the Keyser and Tonoloway Formation. Most of the middle reaches of the watershed are on rock of the Hamilton Group and the uppermost and northernmost reaches of the watershed are on the Trimmers Rock Formation. There are several soil series in the watershed of County Line Branch. The Chenango-Pope-Holly series is found in a small part of the lowest reaches of the lowest reaches of the watershed, near the stream's mouth. The Hagerstown-Edom-Washington series is found in a much larger area in the southern part of the watershed. The Watson-Berks-Alvira series occurs in the watershed's middle reaches and the Berks-Weikert-Beddington series is found near the headwaters and also on its southwestern edge. There is glacial till in the watershed of County Line Branch.
Watershed
The watershed of County Line Branch has an area of 8.97 square miles. Much of the watershed is in Anthony and Limestone Townships in Montour County, but a significant portion of it is in Lewis Township, Northumberland County. The watershed also occupies part of Turbotville. Its northern edge is on the border of Lycoming County. The headwaters of County Line Branch and their vicinity are mostly forested. However, nearly all of the rest of the it is agricultural land. There is little development anywhere in the watershed.