The Shenandoah River flows into the Potomac River at Harpers Ferry, WV. But the Shenandoah River is not the South Branch. The Potomac River is separate from the Shenandoah until they meet at Harpers Ferry. The Potomac flows through what is now several counties in West Virginia. The South Branch of the Potomac flows through Pendleton County, Hardy Co. and Hampshire County. To make it more confusing, there is a North Fork of the South Branch and a South Fork of the South Branch. I'm guess there is a North Branch of the Potomac River somewhere, but I am more familiar with the South Branch. It would be worthwhile to get a detailed WV state map, especially if you are working with deeds. The river description will help narrow down where your ancestor lived. I have a copy of "West Virginia County Maps" by Puetz Place, Lndon Station, WI 53944, but I'm sure there are others. Pat Ritchie