The above sketch shows a view down the length of a side-wheeled steamer sometime during the Civil War.  Steam powered vessels came in to basic varieties during the Civil War: paddle wheeled or screw.  Screw steamers utilized propellers underneath the waterline for propulsion.  Ships like the one shown used large paddlewheels which were not as practical as their cousins with propellers.  In rough weather the paddlewheels could be unwieldy, and during a battle it was much easier to shoot away the large paddles on the side or stern of a ship than a propeller under the waterline.  In the view down this ship, the two large paddlewheels can be seen on either side of the deck.  The smokestacks connected to the ship's boilers below decks can been seen in the center of the deck.  This indeed was a common view for sailors serving on board ships like this during the Civil War, but when acting as transports the vacant deck would have likely been more populated as Army soldiers would have crowded all available space.