The Mississippi River system is in many ways the greatest in the world. The river rises in northern Minnesota in Lake Hernando de Soto beyond Lake Itasca. Its largest tributary is the Missouri River. The Mississippi and Missouri, taken together, are 4,200 miles long. Forty-four tributaries of the Mississippi are navigable. More than $10,000,000 was expended on the construction of this magnificent bridge and the tunnel at its western end. The central span is of 515 feet; it is the largest arch in the United States. The other two main spans are of 497 feet each. The bridge is solidly fixed without hinges on the arches, and high enough for vessels to pass beneath it. The four piers on which the arch rest are built of granite and limestone and rest on the bed-rock of the river. By means of wrought-iron caissons and compressed air they were sunk through the sand from 90 to 120 feet. There are now five bridges across the Mississippi and the Missouri at or near St. Louis. To distinguish it from other bridges and to honour the great engineer who designed and built it, the original St. Louis bridge is now called the Eads Bridge. It was completed in 1874.
