Limestone Run is a tributary of the West Branch Susquehanna River, in Montour County and Northumberland County, in Pennsylvania, in the United States. It is 8.8 miles long and flows through Limestone Township in Montour County and Turbot Township and Milton in Northumberland County. The watershed has an area of 11.6 square miles. Slightly un…Limestone Run is a tributary of the West Branch Susquehanna River, in Montour County and Northumberland County, in Pennsylvania, in the United States. It is 8.8 miles long and flows through Limestone Township in Montour County and Turbot Township and Milton in Northumberland County. The watershed has an area of 11.6 square miles. Slightly under 2,500,000 pounds of sediment flow through the stream annually. The stream's watershed is in the ridge and valley physiographic province.