The United States South Seas Exploring Expedition of 1838-1842 was authorized by Congress in 1836 to observe the Pacific Ocean and South Seas. The four-year voyage — also referred to as the Wilkes Expedition or Ex. Ex. for shorthand — covered an expansive geographic region, including the Pacific Northwest, Fiji Islands, and South America. The expedition was under the command of Lieutenant Charles Wilkes of the Unites States Navy, and the resulting collection is thought to be one of the largest early natural history collections, weighing in at an estimated 40 tons. The collection was transferred to the Smithsonian Institution in 1857 and established what would eventually become the National Museum of Natural History.