St. Louis (English /seɪnt ˈluːɪs/, French /sɛ̃ lwi/) is an independent city in the U.S. state of Missouri. It is bordered by the Mississippi River on the east and by St. Louis County on the north, south, and west. Sometimes written as Saint Louis, the city is named for King Louis IX of France. St. Louis is known for its French and German heritage and Victorian past. Two events at the beginning of the 20th century, the 1904 World's Fair and 1904 Olympic Games (the first ever held in the United States) are of particular pride to St. Louisans. In the 21st century, St. Louis has transformed from a manufacturing and industrial economy into a globally known focus for research in medicine, biotechnology, and other sciences.The city has several nicknames, including the "Gateway City", "Gateway to the West", and "Mound City". It is called "Gateway to the West" for the many people who moved west through St. Louis via the Missouri River (first leg of the Oregon Trail) and other wagon trails. "Mound City" originated with the Native American burial mounds that once were common in the city. These were largely destroyed to level the ground as the city grew. The city is also referred to as "The Lou", "St. Louie", "The Western-Most Eastern City", or "River City". A popular abbreviation for St. Louis is "STL" in reference to the airport code for the city and the long-standing use of an interlocked S, T, and L by the St. Louis Cardinals baseball team (the St. Louis Browns also used an interlocked STL).The City of St. Louis lies at the center of Greater St. Louis, a sprawling region which includes parts of both Missouri and Illinois. The St. Louis MO-IL MSA is the 18th largest metropolitan area in the U.S. with 2,801,033 people as of the July 2006 US Census estimate.