1 Loudoun County Virginia $117,876
2 Howard County Maryland $108,844
3 Fairfax County Virginia $107,096
4 Hunterdon County New Jersey $105,186
5 Arlington County Virginia $100,474
6 Stafford County Virginia $97,606
7 Putnam County New York $96,223
8 Somerset County New Jersey $95,825
9 Douglas County Colorado $95,324
10 Morris County New Jersey $95,294
11 Montgomery County Maryland $94,965
12 Prince William County Virginia $93,744
13 Nassau County New York $93,214
14 Santa Clara County California $91,425
http://en.wikipedia.org/wiki/List_of_highest-income_counties_in_the_United_States
The list is old...2 years old. But I note that three counties in New Jersey come higher on the list than Santa Clara County in California.