Hmm, I can't estimate the profit concerning USA county domain names. Over 3000 counties, some of the names are not registered for .us domain. Americans should say something.
Only in Texas you have additionaly several counties for registration:
Aransas
Bastrop
Brazaria
Comal
Dimmit
JimHogg
Kenedy (sounds nice even with single 'n')
Kleberg
Lavaca