Hi:
I found an 1820 map of Spotsylvania Co. with names of rivers, people, taverns, mills, etc. I did find the North Fork of the North Anna River in the SW corner of the map on the Orange Co. side of Spotsy.
The map is located at:
http://carmichael.lib.virginia.edu/collection/maps/spotsylva...Will keep looking. Hope this helps in some way.
LL