It was but I don't think it is anymore. I remember some county in Wyoming or something passing us. Take Bridgeport out of FC and it probably moves back to the top.
According to Wiki your still top ten per capita.....
1 New York County, New York (Manhattan) $93,377
2 Teton County, Wyoming $89,028
3 Pitkin County, Colorado $77,970
4 Loving County, Texas $77,787
5 Marin County, California $75,884
6 Fairfield County, Connecticut $67,269