What was known as Louisiana Territory comprised most of
modern-day United States between the Mississippi and the
Rocky Mountains, with the exceptions of Texas, parts of New
Mexico, and other pockets of land already controlled by the
United States.

A formal treaty for the Louisiana Purchase, antedated to April
30, was signed two days later.

On April 30, 1812, exactly nine years after the Louisiana
Purchase agreement was made, the first of 13 states to be
carved from the territory—Louisiana—was admitted into the
Union as the 18th U.S. state.