Houston is the fourth-largest city in the United States of America and the largest city within the state of Texas. The brothers Augustus Chapman Allen Augustus and John Kirby Allen founded Houston on August 30, 1836. Houston's economy has a broad industrial base in the energy, manufacturing, aeronautics and technology. The city was incorporated on June 5, 1837 and named after then-President of the Republic of Texas former General Sam Houston. Commercially, Houston is ranked as a world city, and the area is a leading centre for building oilfield equipment. Five major oil refineries are located in Houston (for example Houston Refinery, volume 42.960 m³/d).