"A Washington Post analysis of the latest census data shows that more than a third of Zip codes in the D.C. metro area rank in the top 5 percent nationally for income and education. But what makes the region truly unusual is that so many of the high-end Zip codes are contiguous. They form a vast land mass that bounds across 717 square miles. It stretches 60 miles from its northern tip in Woodstock, Md., to the southern end in Fairfax Station, and runs 30 miles wide from Haymarket in Prince William County to the heart of the District up to Rock Creek Parkway. One in four households in the region are in a Super Zip, according to the Post analysis"