Napoleon Bonaparte was in desperate need of money because he was at war and he was being sued by American farmers, because his men kept persuading the Indians to take there live stock. So Thomas Jefferson Sent Robert R. Livingston and James Monroe to negotiate to buy New Orleans. When they got there they were surprised that Napoleon was offering to sell the all of Louisiana which would double the size of the USA. That is why and how the USA made the Louisiana purchase. Hope this helps.