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I had said, of a presumed map position-
inland, West of the Miss.>

and Jared Sherman asked-

>>George, are your 20 miles based on the current position of the Mississippi?
>>Or the historic position?
>>
>>I have no idea how far it has moved in that area, just that it MOVES a great
>>deal.

===============

No, Jared, not based on the current position, it's based on old mapping, as
evaluated in the recent "Atlas of Lewis and Clark in Missouri" by Harlan
and Denny (2003).

I don't pretend to have any first-hand knowledge about America's great
river systems. Indeed, I've never even seen the Mississippi or the
Missouri. But I know enough about them to say this-

True, the bed of the Mississippi is very mobile, and makes immense and
changing meanders, for natural reasons and at the hands of man. Mark Twain,
in "Life on the Mississippi", describes this process graphically. However,
that applies more to the lower Mississippi, where the river is travelling
through a wide and flat valley.

Between St Louis and the Ohio junction, its character is different. The
flat river valley is constrained between cliffs and high banks, typically 3
to 5 miles apart, where the Mississippi cuts its way through higher ground.
Between those high banks, the river is rather free to writhe about, and its
course has changed somewhat in recorded history, particularly a major
change near Kaskaskia. But these are very minor shifts compared with the
immense loops and cutoffs that occur in the lower river.

Another factor to bear in mind is that this phase of L&C's voyage was
through settled country. Many plots had been already mapped and allocated
by the Spanish, and many more were laid down by the General Land Office
after the Louisiana purchase. Many of those land boundaries exist today.
Harlan and Denny have taken this early survey mapping (just a few years
after L&C) into account when showing the old river-course together with the
present one. I'm not in a position to judge how well that reconstruction
has been done, but it appears to be the best information that's available
at present.

Any comments from those that know the area better than I do (which is not
at all) will be welcome.

George..

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