The Louisiana Territory was about 827,000 square feet, and it doubled the size of the United States. The Louisiana Purchase helped American expansion into the West, and it helped the United States keep control of a major trade port in New Orleans, where ships could come in and out of the land.
To summarize, in 1789,  the French Revolution began and ended in 1799. At this time Spain controlled Louisiana. In 1802, Spain ceded Louisiana back to France, but the Louisiana Purchase place in 1803 During 1804-1806,  the Lewis and Clark expedition started, which expanded our knowledge about North America and how much land it consisted of. A few years later, in 1812, Louisiana officially became a state back to France.
 In 1783, Spain gained Louisiana with the Treaty of Paris. They controlled all of the trade in New Orleans, which is important because New Orleans was a port town, meaning that it was right there. They needed to have access to boats and different things to ship to their people, so controlling a port was a huge deal. If you controlled trade, you made a lot of money. But they ceded Louisiana Territory.
France is led by the dictator, Napoleon. Napoleon thought it cost way too much money to support North American colonies because he was all the way in France. He was fighting a war in Europe and he needed money to support his troops. So he thought the best thing he could do would be to sell the Louisiana Territory back off.
The United States heard this and they sent representatives to ask about buying the port of New Orleans. The reason the wanted to buy it was because they with the port, comes a lot of money. They wanted more territory for a growing population. They also bought Louisiana Territory from France for $15 million.
