Answer:
Napoleon was right in his declaration. The Louisiana Purchase was a very good decision taken by former president Thomas Jefferson.
For a cost of fifteen million dollars, the United States acquired a vast territory that stretched from the Gulf of Mexico to Montana, and from the rocky mountains to the Mississippi River.
The territory of the Louisiana Purchase corresponds to some of the most fertile areas in the nation, and agricultural powerhouse states like Iowa, Nebraska, and Kansas, lie entirely within this territory.
And even more important is the fact that the Louisiana Purchase allowed America to control both the Mississippi and Missouri Rivers, meaning that not only America had a vast territory of great farmland, but also rivers to ship agricultural products.
In conclusion, we can see from these facts that the Louisiana Purchase represented a massive gain for the United States, and was the beginning of its development as a great world power, exactly like Napoleon said.