These are the county codes used by the NC state archives 
to identify the current and former North Carolina counties.  
Thanks to Ann Avery Hunter for posting this to the NCROOTS list.

001...Alamance
002...Albemarle
003...Alexander
004...Alleghany
005...Anson
006...Ashe
007...Avery
008...Bath
009...Beaufort
010...Bertie
011...Bladen
012...Brunswick
013...Buncombe
014...Burke
015...Bute
016...Cabarrus
017...Caldwell
018...Camden
019...Carteret
020...Caswell
021...Catawba
022...Chatham
023...Cherokee
024...Chowan
025...Clay
026...Cleveland
027...Columbus
028...Craven
029...Cumberland
030...Currituck
031...Dare
032...Davidson
033...Davie
034...Dobbs
035...Duplin
036...Durham
037...Edgecombe
038...Forsyth
039...Franklin
040...Gaston
041...Gates
042...Glasgow
043...Graham
044...Granville
045...Greene
046...Guilford
047...Halifax
048...Harnett
049...Haywood
050...Henderson
051...Hertford
052...Hoke
053...Hyde
054...Iredell
055...Jackson
056...Johnston
057...Jones
058...Lee
059...Lenoir
060...Lincoln
061...Macon
062...Madison
063.. Martin
064...McDowell
065...Mecklenburg
066...Mitchell
067...Montgomery
068...Moore
069...Nash
070...New Hanover
071...Northampton
072...Onslow
073...Orange
074...Pamilco
075...Pasquotank
076...Pender
077...Perquimans
078...Person
079...Pitt
080...Polk
081...Randolph
082...Richmond
083...Robeson
084...Rockingham
085...Rowan
086...Rutherford
087...Sampson
088...Scotland
089.. Stanley
090.. Stokes
091...Swaim
092...Surry
093...Transylvania
094...Tryon
095...not assigned
096...Tyrell
097...Union
098...Vance
099.. Wake
100...Warren
101...Washington
102...Watauga
103...Wayne
104...Wilkes
105...Wilson
106...Yadkin
107...Yancey