Marysville is in the central southern part of Campbell County near Seneca and the Pittsylvania Co. line. If you go to Mapquest you can pinpoint it. Also, there is a MrSid Map for Campbell Co. at http://memory.loc.gov/ammem/
. Choose Maps, checkmark all the collections and search Campbell Co. This map has names of families, towns, etc. from the 1860's. Even though your Brown was long gone, there are other Brown families. Census reports might help. This part of Campbell Co. is in the Seneca District.