Ten years ago, you probably could have predicted the richest counties in America, as measured by adjusted gross income. Fairfield County, Conn., topped the list in 2005, followed by Teton County in Wyoming (home of wealthy enclave Jackson Hole), and they were subsequently in the top 5 for the next few years, according to the Transactional Records Access Clearinghouse (TRAC), which collects data from the IRS.
