Why did the US purchase Louisiana?

US wanted Louisiana because they wanted more people to come in to their new states, and they wanted more land for the people that will move in. They also wanted New Orleans because it was profitable, and they wanted to control the Mississippi River. If u own the MS. river that means u own the mouth of it, and u can control who can get in it and/or travel bye it !
The United States purchased this land in order to expand their country. They bought this land from Napoleon (France).