Kirby, the original design of all four forts - A, B, C, and D, was due to the enterprise of Lieutenant John Wesley Powell of the 22nd Illinois, later of the 2nd Illinois Artillery (Light), and commanded Battery F (Powell's Battery) as a Captain at Shiloh. Yes, he's the same one who, after losing his arm at Shiloh, was at Vicksburg and at Franklin. Later he became the first man to lead an expedition own the Colorado River of the Grand Canyon, and was the Second Director of the US Geological Survey.

Originally Gen. Fremont had grandiose designs for fortifications at Cape Girardeau, but Powell's designs were brought to his attention, and were later OKed by Grant.

I highly recommend a trip to Fort D, currently in a city park and semi restored.

And Powell is buried at Arlington National Cemetary. I've chased him all over the country, and learned a lot doing so.