Answer :
After the Mississippi River passes St. Louis it begins to change
character. The river north of St. Louis is punctuated with locks
and dams that allow river boat traffic to navigate the steep
slope that the river follows. South of St. Louis the slope
becomes gentler. At Cape Girardeau, Missouri the river passes
the northernmost point of the Crowley's Ridge.
Crowley's Ridge
delineates the western edge of the Mississippi River Valley
through southeastern Missouri and western Arkansas. The
Mississippi River Valley at this point is called the Mississippi
Embayment and the Crowley's Ridge can be as far as 150 miles
west from the current river channel. When the Mississippi River
meets the Ohio River at Cairo, Illinois it is halfway on its
journey to the sea. It is here that the brown muddy water of the
Mississippi begins to mingle with the clearer water of the Ohio.
On a sunny day you can see the difference from Fort Defiance
Park in Cairo or from Fort Jefferson Hill just south of
Wickliffe, Kentucky. Without the locks and dams the Mississippi
begins to wind and curve so much so that the distance by water
from Cape Girardeau to the Gulf of Mexico is twice the distance
as a crow flies. It is because of this meandering flow that it
is here that the Mississippi begins to take on the moniker of
“Old Man River.”