Southlake has vaulted to the top of the list of the nations richest cities, and neighboring Colleyville is not far behind, according to U.S. Census data released Tuesday.Southlake, a city of more than 26,000, has a median household income of almost $173,000. Colleyville is eighth on the list, at almost $149,000.North Texas, in fact, boasts three of the top 10. University Park, a Dallas suburb, was sixth, at almost $151,500.The data looked at cities with a population of 20,000 or more, which omits cities such as Westover Hills and Highland Park.Median is a household right in the middle.The Texas median is $46,248. Fort Worths median is $44,804.The data comes from the American Community Survey, which collects information such as age, race, income, commute time to work, home value, veteran status, and other data.Other area cities high on the list include:-- No. 59, Keller: $107,518-- No. 63, Coppell: $106,783-- No. 70, Flower Mound: $105,823-- No. 108, Frisco, $96,676.