Jack... a medium to large Black Walnut 'may' be worth something... if you can find a buyer. It is often not profitable for a mill to chase just one tree, unless it is exceptional. Also, many mills shy away from 'urban lumber', as it often has embedded nails or old clothesline hooks.. :>(

In N. Carolina, there are many woodturning clubs, and some might be interested in a decent Walnut. Pecan? Same thing....Pecan is not as common, (I have seen very little)...but not as 'pretty' as Walnut...mostly. If you can find local woodworkers, you might be able to make some deals...or even just trades. Good luck!