Thanks to a high birth rate and brisk immigration, the U.S. population exploded in the first half of the 19th century, from around 5 million people in 1800 to more than 23 mill… See more

Cries for the “re-annexation” of Texas increased after Mexico, having won its … See more

By the time Texas was admitted to the Union as a state in December 1845, the idea that the United States must inevitably expand westward all the way to the Pacific Ocean had … See more

An 1842 treaty between Great Britain and the United States partially resolved the question of where to draw the Canadian border, but left open the question of the Oregon Ter… See more