Read it through once

Seventy years elapsed, after the exploration, before the river's borders had a white population worth considering; and nearly fifty more before the river had a commerce. Between La Salle's opening of the river and the time when it may be said to have become the vehicle of anything like a regular and active commerce, seven sovereigns had occupied the throne of England, America had become an independent nation, Louis XIV. and Louis XV. had rotted and died, the French monarchy had gone down in the red tempest of the revolution, and Napoleon was a name that was beginning to be talked about. Truly, there were snails in those days.