You just can't diminish the part the river played in the Civil War. The waterway itself and the 'Western Campaign' A known drunk (Grant) and a mentally weak little red head (Sherman) turned out to be the two best Generals the Union had, and both exhibited that talent in the Mississippi River campaign.

And the waterway itself. The North set up factories and built 'Ironclads' by the hundreds on the tributaries. That ability to manufacture and produce was the ultimate tipping point for the North.