The bubonic plague caused mass death and it was caused by the lack of sanitation systems throughout medieval towns. The peasants/serfs demanded more and more as the rich people needed more to supply themselves. Eventually, the peasants got a say in government for this. The bubonic plague also caused a lot of the roman empire to die.
"The great Britain made them sail to America."
Erm. It is called "The breakup of Yugoslavia"
:)
What I can infer from what Lewis and Clark saw when moving west from the Mississippi river is that the landscape along the river changed drasticallly. The forest receded, replaced first by the high prairie and then the shorter grass of the high plains. The temperatures became colder and as they continued their expedition by the river they realized that there was no water route to the pacific ocean, just more mountains.
