Marker of Ohio Confluence into the Mississippi:
Lewis was one of the sharpest tools in the tool box. Well educated for the time. Clark, smart but 3rd or 4th grade education. Clark was a trained "Land Surveyor" and had a skill for "dead reckoning"...ability to look at a distance and accurately guestimate the distance. Lewis was self taught how to calculate latitude and longitude from a chrometer(watch), sun, moon and stars. In a 6 day camp, Lewis taught Clark how to calculate Lat & Longitude with these primitive tools. The United States had no maps of the lands west of the Mississippi and Missouri Rivers, and no citizens either. Clark left the below shaded trees and combined his surveyor's skilled with the training from Lewis and the rest is history.
The two captains camped under the below trees to teach Clark how to calculate the measurements:
Trees they camped under:
They left this site on the 7th day, rowed up river on the Mississippi to the Missouri River and the rest is history. Clark was the first to produce a map of lands west of the Mississippi and Missouri Rivers. His map was used by all future explorers, pioneers, and trappers who explored the Western US. With Clarks training, primitive tools, and dead reckoning he was within 27 miles of accuracy from St Louis to the Pacific Ocean. Clark (and Lewis sometimes) religiously documented each day's campsite, scenic event, location of friendly and hostile Indians, future sites for trading post/forts, etc on a daily basic. I've converted Clark's rough coordinates to more like present day more accurate GPS coordinates.
Nearby bridge across the Ohio River: The mace of high bridges over and around these two rivers is pretty amazing. Going up this bridge on two wheels was like climbing a ladder.
Map of where the Ohio and Mississippi Rivers converge: Located in Cairo, Illinois (Just west of Paducah, Ky).