List of companies in Houston  This is an "incomplete" list of major companies or subsidiaries headquartered in Houston, Texas and the Greater Houston metropolitan area. Houston is known for its oil and gas industry, and has the second highest number of Fortune 500 companies after New York City. There are 19 Fortune 500 companies headquartered in Houston. In addition, the Fortune 500 company Huntsman Corporation is headquartered in The Woodlands, Texas, a suburb just north of Houston. In addition to the Fortune 500 companies above, many other companies in multiple fields are headquartered or have based their US headquarters in Houston. Although Exxon Mobil has its corporate headquarters in Irving, Texas, most of its employees are in Houston. Hewlett-Packard maintains a large presence in Harris County. The corporate offices of Imperial Sugar and Minute Maid, a regional headquarters for Unocal 76, and an office of Schlumberger, are based in nearby Sugar Land, Texas. CB&I and US Oncology are based in The Woodlands.