U.S. Population, Land Area and Density, 1790-2020

In the first century of its existence, the United States added regularly to its store of undeveloped land through acquisitions such as the Louisiana Purchaes and conquest, which brought in a great deal of land that had formerly belonged to Mexico. However, the corresponding increases in population resulted in a regular rise in the number of Americans per square mile in every decade except 1810 and 1850, when the aforementioned actions were taken. Even the purchase of Alaska was not able to reverse the increase in density. Since 1870, when the total land area reached about three and a half million square miles, the population density has risen at the same rate as the growth in population.