Louisiana Purchase
The Louisiana Purchase was an 1803 agreement between the United States and France in which the U.S. acquired 828,000 square miles of land for $15 million dollars from Napoleon Bonaparte's French Empire. This territory stretched from the Mississippi River to the Rocky Mountains and doubled the size of America at that time, making it one of history's most significant real estate transactions. The purchase gave rise to several important events in American history, such as Thomas Jefferson's presidency and eventual expansion into western territories.
At first glance, this seems like a good deal for both parties involved; however, there are many implications behind this transaction that will shape US-E European relations in the future years. For example, with France ceding its claim over North America to Britain via treaty negotiations before finalizing their sale with America, they inadvertently weakened Spain's control over their own colonies due south along Mexico's borderlands by creating a new power bloc on their northern doorstep - something that didn't sit well with Madrid or other European capitals at all.
This massive piece of land became known as "the Louisiana Territory" after being named after King Louis XIV (Louisiana) when it was originally claimed by France during colonial times prior to 1762 but had since become part of Spanish rule until 1800, when Napoleon reacquired it from Spain following his victory against them two years earlier during Europe's "War Of The Second Coalition." By purchasing this large swath of land outright rather than through war or conquest, it allowed for a more peaceful settlement compared to how Native Americans were treated elsewhere throughout early US history, thus paving the way towards Manifest Destiny later down the line without much bloodshed or conflict involving indigenous peoples who had already lived there beforehand (at least not directly).