Final answer:
The areas west of the Rocky Mountains, including present-day Texas, were not part of the Louisiana Purchase; this territory was acquired by the U.S. through other means at later dates.
Step-by-step explanation:
The part of America that was not included in the Louisiana Purchase was the land that is present-day Texas and several other western states that were not within the boundaries defined by the deal. The Louisiana Purchase, completed in 1803, doubled the size of the United States by adding the territory west of the Mississippi River and up to the Rocky Mountains. However, it did not include land west of the Rockies, and notably, areas like Texas were not part of the transaction and were later acquired through other means, such as the Texas Annexation and the Adams-Onís Treaty.
President Thomas Jefferson viewed the acquisition as essential for the expansion of the agrarian society he envisioned, as well as for securing control of the Mississippi River and New Orleans, which were crucial for American agricultural commerce. Despite constitutional concerns, Jefferson proceeded with the purchase because the farmable land and control over New Orleans were vital interests of the United States, effectively doubling the nation's size for a total of $15 million, or mere pennies per acre – a historic real estate transaction that supported Jefferson's "empire of liberty."