Houston, the fourth most populous city in the United States and the third-busiest port in the United States, is featured in this southwest-looking, low-oblique photograph. Located 25 miles (40 kilometers) northwest of Galveston Bay (not visible) on the coastal plain, Houston is a great commercial, medical, financial, and industrial hub and is one of the world’s major oil centers. Visible are sediment-laden Lake Houston, the source of much of Houston’s drinking water; the runways of George Bush Intercontinental Airport west of the lake; and the small city of Alvin (upper left). Houston’s continued growth began with the completion of the Houston Ship Channel in 1914.