Final answer:
Thomas Jefferson's goals for Lewis and Clark's expedition were to find an all-water route to the Pacific Ocean, strengthen U.S. claims to the Pacific Northwest through mapping and exploration, document natural resources and establish relations with Native American tribes for trade.
Step-by-step explanation:
Main Goals of Lewis and Clark's Exploration
President Thomas Jefferson tasked Meriwether Lewis and William Clark with a pivotal exploration across the newly acquired Louisiana Territory with three main goals in mind. Firstly, Jefferson hoped the expedition would discover an all-water route to the Pacific Ocean, although this Northwest Passage did not exist. Secondly, the exploration aimed to strengthen U.S. territorial claims, particularly in the Pacific Northwest; this included the establishment of an overland route and mapping of the territory to substantiate legal claims. Lastly, they were to document the territory's natural resources, and wildlife, and establish relations with Native American tribes for future trade.
Their grueling journey still managed to achieve considerable objectives, even though the Northwest Passage remained undiscovered. Lewis and Clark meticulously recorded the geography, flora, and fauna, solidifying the foundation for American scientific understanding and territorial claims. They also opened diplomatic relations with various tribes, an essential step for subsequent traders and settlers.