St. Louis is located at a strategic point where the Missouri River flows into the Mississippi.  It was established in 1764 by French colonists, and under US authority with the Louisiana Purchase in 1803. The city was an important commercial port and the starting point of settlers moving westward into the unsettled areas. Its population rapidly grew with immigrants after 1840, and it hosted the Olympic Games of 1904. The city went into a period of decline in the second half of the 20th century, but nowadays its population is growing again.