Wills Creek is a 38.6-mile-long tributary of the North Branch Potomac River in Pennsylvania and Maryland in the United States. Wills Creek drops off the Allegheny Mountains of southeastern Somerset County, Pennsylvania, beginning on the western slope of Savage Mountain in Larimer Township. It flows into Northampton Township, passing throu…Wills Creek is a 38.6-mile-long tributary of the North Branch Potomac River in Pennsylvania and Maryland in the United States. Wills Creek drops off the Allegheny Mountains of southeastern Somerset County, Pennsylvania, beginning on the western slope of Savage Mountain in Larimer Township. It flows into Northampton Township, passing through Mance, Philson Station, and Glencoe. Wills Creek continues into Fairhope Township, passing through Foley, Fairhope, and Williams Station on its course eastward. Wills Creek enters Bedford County, Pennsylvania, in Londonderry Township, passing through Hyndman and making a sharp turn southward. It crosses from Pennsylvania into Maryland near Ellerslie in Allegany County, Maryland. It then runs past Corriganville and near Narrows Park before entering the North Branch Potomac River at Cumberland, Maryland.