Also, do you know what side these men served? There is one William H.King serving the Federals, 6 William H. King serving the Confederacy. None were listed from Warren County, NC, although three of the seven do not have their home county detailed. Might do some further tracking if you can provide his age, or pre/post war occupation.
No record of a Willam Riggan in the US, and none in CS service. There are records of 16 Riggans from Warren County serving the Confederacy, but no William. There is a Sugar Riggan, any Sugars in your line?