Houston is the fourth largest city in the United States located in southeast Texas . The city is the county seat of Harris County and the third most populous county in the country. According to the 2000 census, the city had a total population of 1,953,631. Houston is one of the two largest economic areas in Texas . A far Southwest portion of Houston extends into Fort Bend County . Houston is among the most recent and fastest growing major cities in the United States . In 1900, Houston had a population of about 45,000, and it was the 85th largest town in the U.S. Presently with 5 million people residing in Houston Metropolitan Area it is quoted as " Fastest Growing City in America " and "the Most Popular City to Relocate”. Houston is spread over a total area of 600 square miles and is also the largest city in the United States that does not have zoning laws. Houston is famous all over the world for its energy industry (mainly oil), aeronautics industry and ship channel. This makes the port of Houston one of the busiest ports in the United States and second in the world in regard of foreign tonnage. Officially, Houston has been nicknamed the Space City . " Houston " was the first word spoken on the moon when Neil Armstrong reported back to NASA. George Bush Intercontinental Airport (IAH) and William P. Hobby Airport (HOU) serve Houston for its air transport. Bush Airport takes care of the city's international traffic. Houston had several growth spurts in context to the Texas oil industry. In the 1920s, Houston had the first growth spurt. The second growth gush of the city took place in the 1970s, with the Arab Oil Embargo. As the requirement for Texas oil increased people from the northeast came down to profit from the trade. When the restriction was lifted, the growth stopped. Houston has attempted to build a banking industry in the city, but all of the companies, which had been started in Houston , were merged with other companies nationwide. Real Estate is also a large business in the Houston area. The city has the second lowest living cost in comparison to other major U.S. cities. The housing in Houston is also quite affordable.