The Lewis and Clark Exposition dollar was a commemorative gold coin struck in 1904 and 1905 as part of the United States Government's participation in the Lewis and Clark Centennial Exposition, held in the latter year in Portland, Oregon. Designed by United States Bureau of the Mint Chief Engraver Charles E. Barber, the coin did not sell well and less than a tenth of the authorized mintage of 250,000 was issued. The Lewis and Clark Expedition, the first American overland exploring party to reach the Pacific Coast, was led by Meriwether Lewis and William Clark. Between 1804 and 1806, its members journeyed from St. Louis to the Oregon coast and back, providing information and dispelling myths about the large area obtained by the United States in the Louisiana Purchase of 1803. The Portland fair commemorated the centennial of that trip. The coins were, for the most part, sold to the public by numismatic promoter Farran Zerbe, who had also vended the Louisiana Purchase Exposition dollar. As he was unable to sell much of the issue, surplus coins were melted by the Mint. The coins have continued to increase in value, and today are worth between hundreds and thousands of dollars, depending on condition. The Lewis and Clark Exposition dollar is the only American coin to be "two-headed", with a portrait of one of the expedition leaders on each side.