Houston is the most populous city in the U.S. state of Texas and fourth-most populous city in the United States, with an estimated 2019 population of 2.3 million. Comprising a total area of 637.4 square miles (1,651 km2), Houston is the largest city in the United States by total area, whose government is not consolidated with that of a county, parish, or borough. Houston has become a global city, with strengths in culture, medicine, and research.