FACTBOX: Houston, Galveston in path of Hurricane Ike

(Reuters) - Hurricane Ike closed in on the Texas coastal cities of Houston and Galveston on Friday, threatening both with wall of water that could inundate low-lying areas.

The massive storm surge had the potential to swamp refineries along the Gulf Coast that process about 20 percent of the nation's fuel.

Here are some facts about the affected areas:

HOUSTON

* Fourth largest U.S. city with population of 2.2 million; sixth largest U.S. metropolitan area with about 5.6 million people

* Port of Houston on Galveston Bay is key crude oil import entry and tenth largest world port.

* Downtown is about 50 feet above sea level

* Administrative hub of U.S. oil industry

* The area is home to NASA's Johnson Space Center, the Mission Control Center for U.S. space shuttle flights.

* In 1961 Hurricane Carla hit a much less developed Houston as a Category 4 and caused more than $2 billion in damage and 43 deaths.

GALVESTON

* Population of nearly 60,000. Considered part of the Houston metropolitan area

* Galveston Island, where the city of Galveston is located, is a barrier island on the Gulf coast, 50 miles southeast of Houston. Island averages 2 miles wide and is about 27 mile long and 20 feet above sea level at its highest point.

* Port of Galveston on the Gulf Intracoastal Waterway, the north side of Galveston Island, handles cargo and is a passenger cruise ship terminal.

* Mandatory evacuation ordered.

* Site of deadliest weather disaster in U.S. history, the hurricane of 1900, which brought a storm surge that covered most of Galveston. At least 6,000 people died.

GULF COAST PETROLEUM INDUSTRY

* U.S. Gulf of Mexico is home to a quarter of U.S. crude oil production and 15 percent of natural gas production.

* More than a third of U.S. oil refinery capacity located from Mississippi to Texas. The Exxon Mobil facility in Baytown, near Houston, is the largest refinery in the United States.