I descend from Cornelia van Zandt who married Lucas  Covert. I am related to threw Mary Covert. Mary, their daughter married William McNees who is the son of William McNees who is the son of William and Jane McCormack McNees.

Mary Covert and William McNees had Marcus McNeice.

Cornelia van Zandt was born 15th May 1738 in New Jersey and died in Butler County, Pennsylvania. She was baptised on the 15th of May 1746
Her father was Peter Praa van Zandt and Sarah Willemszen.
I do not know if I am right-I am not claiming that what you have about the history of the McNees's are wrong. I just thought because a river in germany is called the River Neisse which is the current boarder of germany is the origins of the Clan MacNies is kind of weak.
I thought McNees is Americanized due to the sensus people trying to figure out how to spell Gaelic names back then. Though, MacNiec is a sept of the Clan MacGregor and the MacNiecs where beaten in a fierce battle way long time ago in scotland over clan wars and territory and only a few were left that lived on a Island. Those remaing McNees's were soon there after killed except for one by the clan MacNab? That remaining McNees is known as the father of all american McNees/MacNiec/McKnees etc I have seen McKnees as that i have ancestors whose siblings spelled their name that way in the turn of the last century.
http://www.electricscotland.com/webclans/m/macgreg2.html  is where i got the history of the McNees. I am not trying to be a smarty or nothing. I just say Cornelia vanzandt covert mcnees on your site who moved to Ireland or something which i know is not accurate.
I bid you all good luck in the family research, i myself am finding more and more on the McNees/MacNiec's all the time , being related to them myself threw alot of Scottish lines like the MacMillans, MacCormicks, Leslie and Campbell
Philip O'Duibne Campbell