Houston is home to the corp. headquarters for fortune 500 companies. As a matter of fact you are not even considered a large company if you do not have representation in Houston.
Houston is one of the largest cities in Texas (which is large enough to be a country). Mony of these companies are the makers and breakers of politicians, presidential candidates, and powers that run world economies. Houston downtown office rates are among the top six priciest in the country. Enron and Reliant are two energy companies, both participating in the downtown skyline, though Enron has been surrounded with controversy and may not survive.