The Land Act of 1820 (enacted April 20, 1820) eliminated the purchase of public land in the United States on credit. It also reduced the minimum size of the tract from 160 to 80 acres (647,000 to 324,000 m²). Additionally, the act required a down payment of $100.00 and reduced the price from $1.65 to $1.25 per acre ($408 to $309/km²). The land was located in the Northwest and Missouri Territories (at that time referred to as the West).

The act was instrumental in ushering in a new age of Western influence. The low price made it possible for settlers to move to the West, thus increasing the population in the West, and with it, Senate seats from the eventual states.