Too many Pattersons!

My gg grandfather was a William Patterson born about 1810-1812 in western PA. One biographical sketch of his son, Thomas Newton Patterson, DDS indicates that William was born in Westmoreland County where "he grew to manhood and for some years was a millwright". While William was in Ohio by 1847, I have a letter which indicates other Patterson family members remained in western PA. The letter was written by his nephew John M. Patterson, and references family "on" Turtle Creek and Deer Creek.

For any of you who've looked into the Patterson lines, here is the common problem. There are simply too many Pattersons, all with the same names, to easily sort out. In starting with the 1820 census, and trying to qualify families based on the presence of a son under 10 years of age, or between 10-15, I have 8 qualifying Patterson families in Westmoreland County, and about 24 qualifying Patterson families in Allegheny County.

I'm thinking that my best approach might be to rule out other well documented lines in order to narrow the options before I begin my own original research.  Comments, advice, or referrals are welcome.