What did the Transcontinental Treaty achieve?

The Transcontinental Treaty, also known as the Adams-Onís Treaty, was signed in 1819 and primarily achieved the cession of Florida from Spain to the United States. This treaty was significant because it not only allowed the U.S. to acquire Florida but also delineated the boundary between Spanish territory and the United States. It resolved longstanding tensions over territorial disputes and allowed the U.S. to expand its reach toward westward territories.

While the other options present important aspects of American history and territorial expansion, they do not accurately describe the key achievement of the Transcontinental Treaty. For instance, the control of Texas was not a product of this treaty but rather involved later conflicts and negotiations. Similarly, the establishment of trade routes to Asia was not a direct result of the treaty, and while military alliances have been formed with Spain at various times, this treaty focused more on territorial cessions and boundaries rather than military cooperation. Overall, the acquisition of Florida marked a critical step in America's territorial expansion during the early 19th century.