Columbus, Kentucky, has a park where you can see not only some guns deployed to block the navigation of the Mississippi, but also part of a chain erected across the river. The pictures also show how easy it was to control navigation on the Mississippi by observing from the heights. Interestingly, it appears the park was a product of Franklin Delano Roosevelt's WPA, a make-work scheme to inject money into the U.S. economy during the Great Depression.
The fortifications were under the immediate command of one of the more incompetent generals of the Civil War, the much-loved Leonidas Polk. Polk had sent one of his subordinates to occupy the place in September 1861, a decision that was arguably the most disastrous made by any Rebel commander during the war. That it was perceived as problematic at the time is clear from this exchange with the governor of Tennessee preserved in the Official Records. It had the consequence of forcing Kentuckians to take sides in a war they really preferred to avoid, and most of them opted for the Union. Read on, to see what President Davis tersely had to say about it.
Polk was forced to withdraw from the bastion after General Ulysses Grant had performed his masterful campaign to capture Forts Henry and Donelson, to the southwest of Columbus along the Cumberland and Tennessee rivers. This led to the occupation of Nashville by Union forces. Faced with the prospect of Columbus's garrison being cut off by the advancing Union forces, the Rebel commander of the area, General Albert S. Johnston, ordered Polk to a concentration of forces at Corinth, Mississippi, before he made an attack on Grant's position at Shiloh.
Hat tip to Battlefield Biker.