What effect did the addition of the louisiana purchase have in land size in the united states?

It doubled the size of the United States

Explanation:

Lousiana was a huge territory that expanded from the great lakes to the Gulf of Mexico. It included a large part of the Mississippi River and part of the Rocky mountains. This vast expanse of land blocked the US expansion to the west.

The territory became 15 states and represented one of Jefferson's most significant contributions to the United States. Control of the Mississippi also guaranteed the protection of commercial routes north-south and access to the central valleys and the rocky mountains.

the answer is states.