The Rappahannock Forge was located in Falmouth, VA, Stafford County, just across the Rappahannock river, north of Fredericksburg. The Fredericksburg Manufactory was supposedly located in Fredericksburg, VA. It's my understanding that the Manufactory was a State founded operation, the Rappahannock Forge was privately operated. The Rappahannock Forge was a huge operation by the days standards, and they produced arms for the Continental Army. I believe the forge was owned by James Hunter, Frederick Klette was the supervisor of operations.
There are a handful of muskets from the Rappahannock Forge that have survived. I have a book around here someplace on the Rappahannock Forge, I'll search around and see if I can come up with it...
Ed