In 1792, Thomas Jefferson, principal author of the Declaration of Independence, will claim that the Doctrine of Discovery is international law, and is applicable to the new United States government.
He will become the United States president in 1801.
In 1803, Jefferson acquires the Louisiana Territory from France and sends a secret message to Congress, asking for $2500 to fund an expedition all the way to the Pacific. He assigns Meriwether Lewis and William Clark and the Corps of Discovery to the task.
He hopes this will expand trade, but also, he wants to stop any other European countries from colonizing the western frontier.