How many years were there between the Lousiana Purchase and its exploration?

Answer 1

I posted twice on accident

Answer 2

Native Americans had been exploring this region for thousands of years. Europeans explored it in the 1600s and 1700s.

However, the Lewis and Clark Expedition was the first "official" exploration and started just months after the purchase of this territory.

http://www.enchantedlearning.com/history/us/1800/louisianapurchase/