— Great River Road Minnesota —
Front
Ever since Americans recognized the Upper Mississippi River's potential as a transportation route, they have been trying to improve it for commercial navigation. One such improvement, Lock and Dam No.7, is visible from this site.
This lock and dam, built between 1934 and 1937 by the U.S. Army Corps of Engineers, is one of 29 between Minneapolis and St. Louis. Designed to keep the depth of the main channel from falling
below nine feet, these structures have tamed the once-wild river, effectively transforming it into a long, long stairway.
Wing Dams and Closing Dams
The first attempt to improve the Upper Mississippi for navigation began in 1878, when Congress authorized the Corps to create a continuous four-foot channel from St. Paul to the mouth of the Ohio River at Cairo, Illinois. To accomplish this, the Corps constructed hundreds of wing dams -long, thin piers of rock that jutted out from one shore or the other- and closing dams, which resembled wing dams but ran from shore to island or island to island.
In 1907, the minimum channel depth was increased to six feet, and even more wing and closing dams were built. By 1930,when Congress authorized a nine-foot channel, more than 1,000 of these simple dams had been installed.
Wildlife Habitat Suffered
By constricting
the river's flow, the wing and closing dams eliminated many side channels and backwaters that provided habitat for wildlife. The modern lock and dam system has submerged most of these older dams, including the ones on this stretch of the river, thereby reflooding backwater areas. But because the river is no longer free to meander, many of these areas are gradually being filled with sediment.
The Mississippi River is 3800 km (2,350 miles) long
of which 1050 km (660 miles) are, in Minnesota. These
are approximate measurements, for the river cuts new
channels from time to time.
The lock and dam system has been a boon to commercial
navigation. River commerce, less than one million tons a
year in the mid-1920s, now exceeds 70 million tons annually.
Between Lake Itasca and the Gulf of Mexico, the Mississippi River
descends 454 m (1,488 feet). More than half of that drop 261 m
(857 feet) - occurs before the river reaches the Iowa border.
Back
On the Water
Down through the years, many kinds of boats have travelled the Mississippi River, carrying passengers and freight upstream, downstream, or from one shore to the other. Here are five of the most common on this part of the river.
Birchbark Canoe (Pre-European Settlement - 1800)
Ferryboat (1840 - 1900)
Keelboat (1805 - 1840)
Steamboat (1823 - 1900)
Barge
(1900 - Present)
Comments 0 comments