The principal ports on or near the Gulf are New Orleans in Louisiana, Mobile in Alabama, and Galveston in Texas. Tallahassee and Apalachicola, in Florida, also carried on a brisk trade in cotton at the time of the secession. By far the best harbor is Pensacola Bay, in Florida, near the Alabama line. The town was not at that time a place of much commerce, on account of defective communication with the interior; but the depth of water, twenty-two feet, that could be carried over the bar, and the secure spacious anchorage within made it of great value as a naval station. It had been so used prior to the war, and, although falling at first into the hands of the Confederates, was shortly regained by the Union forces, to whom, from its nearness to Mobile and the passes of the Mississippi, as well as from its intrinsic advantages, it was of great importance throughout the contest. The aim of the National Government in connection with this large expanse of water and its communications was two-fold. First, it was intended to enter the Mississippi River from the sea, and working up its stream in connection with the land forces, to take possession of the well-known positions that gave command of the navigation. Simultaneously with this movement from below, a similar movement downward, with the like object, was to be undertaken in the upper waters. If successful, as they proved to be, the result of these attacks would be to sever the States in rebellion on the east side of the river from those on the west, which, though not the most populous, contributed largely in men, and yet more abundantly in food, to the support of the Confederacy. The second object of the Government was to enforce a strict blockade over the entire coast, from the Rio Grande to Florida. There were not in the Confederate harbors powerful fleets, or even single vessels of war, which it was necessary to lock up in their own waters. One or two _quasi_ men-of-war escaped from them, to run short and, in the main, harmless careers; but the cruise that inflicted the greatest damage on the commerce of the Union was made by a vessel that never entered a Southern port. The blockade was not defensive, but offensive; its purpose was to close every inlet by which the products of the South could find their way to the markets of the world, and to shut out the material, not only of war, but essential to the peaceful life of a people, which the Southern States were ill-qualified by their previous pursuits to produce. Such a blockade could be made technically effectual by ships cruising or anchored outside; but there was a great gain in actual efficiency when the vessels could be placed within the harbors. The latter plan was therefore followed wherever possible and safe; and the larger fortified places were reduced and occupied as rapidly as possible consistent with the attainment of the prime object--the control of the Mississippi Valley.