populations greater than 600,000 people. Austin, Fort Worth, and El Paso are among the 20 largest U.S. cities. Texas has four metropolitan areas with populations greater than a million: , , , and . The Dallas–Fort Worth and Houston metropolitan areas number about 7.5 million and 7 million residents as of 2019, respectively. Three interstate highways—I-35 to the west (Dallas–Fort Worth to San Antonio, with Austin in between), I-45 to the east (Dallas to Houston), and I-10 to the south (San Antonio to Houston) define the Texas Urban Triangle region. The region of contains most of the state's largest cities and metropolitan areas as well as 17 million people, nearly 75 percent of Texas's total population. Houston and Dallas have been recognized as world cities. These cities are spread out amongst the state. In contrast to the cities, unincorporated rural settlements known as colonias often lack basic infrastructure and are marked by poverty. The office of the Texas Attorney General stated, in 2011, that Texas had about 2,294 colonias, and estimates about 500,000 lived in the colonias. Hidalgo County, as of 2011, has the largest number of colonias. Texas has the largest number of people living in colonias of all states. Texas has 254 counties, which is more than any other state by 95 (Georgia). Each county runs on Commissioners' Court system consisting of four elected commissioners (one from each of four precincts in the county, roughly divided according to population) and a county judge elected at large from the entire county. County government runs similar to a "weak" mayor-council system; the county judge has no veto authority, but votes along with the other commissioners. Although Texas permits cities and counties to enter "interlocal agreements" to share services, the state does not allow consolidated city-county governments, nor does it have metropolitan governments. Counties are not granted home rule status; their powers are strictly defined by state law. The state does not have townships—areas within a county are either incorporated or unincorporated. Incorporated areas are part of a municipality. The county provides limited services to unincorporated areas and to some smaller incorporated areas. Municipalities are classified either "general law" cities or "home rule". A municipality may elect home rule status once it exceeds 5,000 population with voter approval. Texas also permits the creation of "special districts", which provide limited services. The most common is the school district, but can also include