Was it true in 1803 the Louisiana territory became part of the U.S?

Yes, it is true that in 1803, the Louisiana Territory became part of the United States through the Louisiana Purchase. This acquisition, negotiated by President Thomas Jefferson, involved the U.S. purchasing approximately 828,000 square miles of territory from France for $15 million. The purchase significantly expanded the U.S. territory and paved the way for westward expansion.