The method of inland navigation by means of slackwater formed by dams passable by locks was early proposed for the Ohio River after the first experiment made of this method on the Green River, Kentucky, in 1834–36 by Chief Engineer Roberts. The successful operation of this system on the Monongahela and Muskingum Rivers exerted a powerful influence in its favor, and for many years its adoption on the Ohio was urged patiently though unsuccessfully. At last the important matter was advocated with success, and in 1885 the first of a series of locks and movable dams was erected at Davis Island, four and one-half miles below Pittsburg. The work now is rapidly being completed, the plan being to give a minimum depth of six feet of water in the Ohio by means of thirty-eight dams and locks between Pittsburg and the mouth of the Great Miami, below Cincinnati. This form of improvement will of course be extended in time to the mouth of the Ohio.
From past experience with dams in the river, the cost of locks is estimated as follows:
