The United States Exploring Expedition (1838–1842) was an exploring and surveying expedition of the Pacific Ocean ("the Southern Seas") conducted by the United States Navy to learn more about the Pacific Ocean and its ports. The expedition with five ships was authorized by Congress in 1836. It is sometimes called the "Ex. Ex." for short, or "the Wilkes Expedition" in honor of its next appointed commanding officer, U.S. Navy Lt. Charles Wilkes (1798–1877). The expedition was of major importance to the growth of oceanography and cartography of the Pacific. Two of these ships were lost from accidents—one on the Columbia River in 1841. From the area of modern-day Portland, Oregon, an overland party headed by George F. Emmons was directed to proceed via an inland route to San Francisco Bay. This Emmons party traveled south along the Siskiyou Trail, including the Sacramento River, making the first official recorded visit by Americans to and scientific note of Mount Shasta, in northern California. The Emmons party rejoined the ships, which had sailed south, in San Francisco Bay. After their return Wilkes published the major scientific works "Western America, including California and Oregon" (1849) and "Theory of the Winds" (1856).