There were 7 nearly identical ships built by Eads at Cairo and St. Louis, Missouri. They were shallow draft, driven by centered paddle wheels, and only partially armored. They were slow, hard to handle in the currents of the rivers, and vulnerable to plunging fire and hits in their un-armored areas, but they did yeoman service through 4 years of war.
Also called "Pook Turtles" for the man who designed them. They were present at nearly every battle on the Mississippi and it's tributaries.
The battles included Fort Donelson, Fort Henry, Island No. 10, Ft. Pillow, Memphis, Vicksburg, the battles vs. CSS Arkansas, and the ill-fated Red River expedition to name a few.