The Clark Bridge, linking Illinois and Missouri at Alton, is a cable-stay bridge, unique in its structure in the United States. The bridge is named for explorer William Clark, who helped lead the Lewis & Clark Corps of Discovery expedition from 1804 to 1806. The bridge is a 4,620 foot gateway inviting visitors to discover the region. Requiring 8,100 tons of structural steel, 44,100 cubic yards of concrete and more than 160 miles of cable wrapped with four acres of yellow plastic piping, the Clark Bridge is expected to be a part of the area's scenery well into the next century. The bridge is supported by 44 steel cables looped over saddles and perched on top of a pair of ten foot wide concrete pylons 250 feet above the Mississippi River. Design work on the bridge began in 1985, with construction starting in June 1990. The span carries four lanes of traffic and two additional paths for bicycles and pedestrians.