III.

Headwaters to Missouri

The Mississippi rises in the area of Lake Itasca in north-western Minnesota, about 512 m (1,680 ft) above sea level. As it issues from Lake Itasca the Mississippi is about 3.7 m (12 ft) wide and 0.5 m (1.5 ft) deep. The upper course of the river is steep and at times obstructed by winter ice and fog. Steep bluffs of sandstone and limestone flank much of the river in this section. It flows north-east and then turns south near Grand Rapids, Minnesota. At Minneapolis, where it drops 20 m (65 ft) over the Falls of St Anthony, the river is more than 305 m (1,000 ft) wide. This point is the head of river navigation on the Mississippi. After receiving the waters of the Minnesota and St Croix rivers, the Mississippi becomes the boundary between the states of Minnesota, Iowa, Missouri, Arkansas, and Louisiana on the west, and Wisconsin, Illinois, Kentucky, Tennessee, and Mississippi on the east.

On the Wisconsin boundary the river expands into Lake Pepin, and thereafter, with a width of about 1.6 km (1 mi), flows between bluffs 61 and 91 m (200 and 300 ft) high. Around obstructions to navigation at Rock Island, Illinois, Keokuk, Iowa, and north of St Louis, Missouri, the US government has constructed dams and locks to accommodate the thousands of barges carrying bulk commodities up and down the river.

Devastating floods above Cape Girardeau, Missouri, extending as far north as Wisconsin, still occur every decade or so, most notably in 1937, 1965, 1973, 1983, and 1993. The floods inundate some river towns and cities, destroy millions of acres of crops, and halt commercial river traffic. The 1993 flood is estimated to have caused US$10 billion of damage.