The United States' southern neighbor, Mexico is about a quarter as large with about a third as large a population. (A little bit bigger than a third as large as the lower-48.) It is a rich agricultural country, also with abundant natural resources including oil, and with an extremely varied indigenous Indian population. Colonized by the conquistadors in the 16th Century, Mexico was the battleground for several major earlier civilizations including the Aztecs and Mayans. The country has a vibrant democracy and a very close association with the United States.