some historical perspective (mllg)

Until the Louisiana purchase, settlement beyond the Mississippi was illegal for american pioneers. that was indian territory.

with the Louisiana purchase in 1803, Jefferson interpreted his purchased territory as all the area draining into the Mississippi. If you look at a map, you will see that the Missouri river, which drains into the Mississippi, transits all the way from Northern Idaho to the Mississippi just north of St. Louis. Jefferson had effectively purchased the entire northwest of the current US, excluding Oregon. (idaho, montana, wyoming, n dakota, s. dakota, nebraska, kansas, missouri, iowa, wisconsin, minnesota, wisconsin... did i forget any?)

Strategically, the Louisiana purchase was probably the most influential act in American history (second only to the Declaration of Independence) because it allowed a two ocean country. Spain and Britian still had to be contended with, but putting the Missippi and the Missouri under US sovereignty, allowed the passage of people and trade to the water port of New Orleans without foreign intervention.

the opening of the west was quickly followed by railway construction, the homesteading acts and the largest migration of peoples in the history of the world. people from all over came to the US to get free land and become part of the american dream.