| Name. | Tons. | Guns. | Commanding Officer |
| Screw Sloops. | |||
| Hartford | 1990 | 24 | Flag-Officer David G. Farragut. Fleet-Captain Henry H. Bell. Commander Richard Wainwright. |
| Pensacola | 2158 | 23 | Captain Henry W. Morris. |
| Brooklyn | 2070 | 22 | Captain Thomas T. Craven. |
| Richmond | 1929 | 24 | Commander James Alden. |
| Side-Wheel. | |||
| Mississippi | 1692 | 17 | Commander Melancton Smith. |
| Screw Corvettes. | |||
| Oneida | 1032 | 9 | Commander S. Phillips Lee. |
| Varuna | 1300 | 10 | Commander Charles S. Boggs. |
| Iroquois | 1016 | 7 | Commander John De Camp. |
| Screw Gunboats. | |||
| Cayuga | 507 | 2 | Commander Napoleon B. Harrison. |
| Itasca | 507 | 2 | Lieutenant C.H.B. Caldwell. |
| Katahdin | 507 | 2 | Lieutenant George H. Preble. |
| Kennebec | 507 | 2 | Lieutenant John H. Russell. |
| Kineo | 507 | 2 | Lieutenant George M. Ransom. |
| Pinola | 507 | 2 | Lieutenant Pierce Crosby. |
| Sciota | 507 | 2 | Lieutenant Edward Donaldson. |
| Winona | 507 | 2 | Lieutenant Edward T. Nichols. |
| Wissahickon | 507 | 2 | Lieutenant Albert N. Smith. |
About ninety per cent. of the batteries of the eight larger vessels were divided, as is usual, between the two sides of the ship, so that only one half of the guns could be used at any one time, except in the rare event of having an enemy on each side; and even then the number of the crew is based on the expectation of fighting only one broadside. A few guns, however, varying in number in different ships, were mounted on pivots so that they could be fought on either side. In estimating the number of available guns in a fleet of sea-going steamers of that day, it may be roughly said that sixty per cent. could be brought into action on one side. In the Mississippi Squadron sometimes only one-fourth could be used. To professional readers it may seem unnecessary to enter on such familiar and obvious details; but a military man, in making his estimate, has fallen into the curious blunder of making a fleet fire every gun, bow, stern, and both broadsides, into one fort, a hundred yards square; a feat which only could be performed by landing a ship in the centre of the works, in which case it could enjoy an all-round fire. The nine gunboats carried one heavy and one light gun, both pivots and capable of being fought on either side. None of this fleet could fire right ahead. All the vessels were built for ships of war, with the exception of the Varuna, which was bought from the merchant service.[2]
The mortar-schooners each carried one XIII-inch mortar. Of the six gunboats attached to this part of the expedition, one, the Owasco, was of the same class as the Cayuga and others. The Clifton, Jackson, and Westfield were large side-wheel ferry boats, of the ordinary double-ended type; carrying, however, heavy guns. They were powerful as tugboats and easily managed; whereas the Miami, also a double-ender, but built for the Government, was like most of her kind, hard to steer or manœuvre, especially in a narrow stream and tideway. The sixth was the Harriet Lane, a side-wheel steamer of 600 tons, which had been transferred from the Revenue Service.
The tonnage and batteries of these steamers were:[3]
| Name. | Tons. | Guns. | Commanding Officer | |
| Screw Gunboat. | ||||
| Owasco | 507 | 2 | Lieutenant John Guest. | |
| Paddle-Wheel Steamers. | ||||
| Westfield | Double-enders. | 891 | 6 | Commander William B. Renshaw. |
| Miami | 730 | 5 | Lieutenant A. Davis Harrell. | |
| Clifton | 892 | 7 | Lieutenant Charles H. Baldwin. | |
| Jackson | 777 | 7 | Lieutenant Selim E. Woodworth. | |
| Harriet Lane | 619 | 3 | Lieutenant Jonathan M. Wainwright. | |
When the ships were inside, the flag-officer issued special instructions for their preparation for the river service. They were stripped to the topmasts, and landed all spars and rigging, except those necessary for the topsails, jib, and spanker. Everything forward was brought close in to the bowsprit, so as not to interfere with the forward range of the battery. Where it could be done, guns were especially mounted on the poop and forecastle, and howitzers placed in the tops, with iron bulwarks to protect their crews from musketry. The vessels were ordered to be trimmed by the head, so that if they took the bottom at all it would be forward. In a rapid current, like that of the Mississippi, a vessel which grounded aft would have her bow swept round at once and fall broadside to the stream, if she did not go ashore. To get her pointed right again would be troublesome; and the same consideration led to the order that, in case of accident to the engines involving loss of power to go ahead, no attempt should be made to turn the ship's head down stream. If the wind served she should be handled under sail; but if not, an anchor should be let go, with cable enough to keep her head up stream while permitting her to drop bodily down. Springs were prepared on each quarter; and, as the ships were to fight in quiet water, at short range, and in the dark, special care was taken so to secure the elevating screws that the guns should not work themselves to too great elevation.
In accordance with these instructions the ships stripped at Pilot Town, sending ashore spars, boats, rigging, and sails; everything that was not at present needed. The chronometers of the fleet were sent on board the Colorado. The larger ships snaked down the rigging, while the gunboats came up their lower rigging, carrying it in and securing it close to the mast. The flag-ship being now at the Head of the Passes remained there, the flag-officer shifting his flag from one small vessel to another as the requirements of the squadron called him to different points. A detachment of lighter vessels, one of the corvettes and a couple of gunboats, occupied an advance station at the "Jump," a bayou entering the river on the west side, eight miles above the Head of the Passes; the enemy's gunboats were thus unable to push their reconnoissances down in sight of the main fleet while the latter were occupied with their preparations. The logs of the squadron show constant bustle and movement, accompanied by frequent accidents, owing to the swift current of the river, which was this year exceptionally high, even for the season. A hospital for the fleet was established in good houses at Pilot Town, but the flag-officer had to complain of the entire insufficiency of medical equipment, as well as a lack of most essentials for carrying on the work. Ammunition of various kinds was very deficient, and the squadron was at one time threatened with failure of fuel, the coal vessels arriving barely in time.
The first and at that time the only serious obstacle to the upward progress of the fleet was at the Plaquemine Bend, twenty miles from the Head of the Passes, and ninety below New Orleans. At this point the river, which has been running in a southeasterly direction, makes a sharp bend, the last before reaching the sea, runs northeast for a mile and three-quarters, and then resumes its southeast course. Two permanent fortifications existed at this point, one on the left, or north bank of the stream, called Fort St. Philip, the other on the right bank, called Fort Jackson. Jackson is a little below St. Philip, with reference to the direction of the river through the short reach on which they are placed, but having regard to the general southeast course, may be said to be lower down by 800 yards; the width of the river actually separating the faces of the two works. At the time the fleet arrived, the woods on the west bank had been cleared away below Jackson almost to the extreme range of its guns, thus affording no shelter from observation; the east bank was nearly treeless. Extending across the river from below Jackson, and under the guns of both works, was a line of obstructions which will be described further on.
The works of St. Philip consisted of the fort proper, a structure of brick and earth mounting in barbette four VIII-inch columbiads and one 24-pounder; and two water batteries on either side of the main work, the upper mounting sixteen 24-pounders, the lower, one VIII-inch columbiad, one VII-inch rifle, six 42-pounders, nine 32s, and four 24s. There were here, then, forty-two guns commanding the river below the bend, up which the ships must come, as well as the course of the stream in their front. Besides these there were one VIII-inch and one X-inch mortar in the fort; one XIII-inch mortar, whose position does not appear; and a battery of four X-inch sea-coast mortars, situated below and to the northeast of the lower water battery. These last pieces for vertical shell-firing had no influence upon the ensuing contest; the XIII-inch mortar became disabled at the thirteenth fire by its own discharge, and the X-inch, though 142 shell were fired from them, are not so much as mentioned in the reports of the fleet.
Fort Jackson, on the southern bank of the bend, was a pentagonal casemated work, built of brick. In the casemates were fourteen 24-pounder smooth-bore guns, and ten flanking howitzers of the same calibre. Above these, in barbette, were two X-inch and three VIII-inch columbiads, one VII-inch rifle, six 42-pounders, fifteen 32s, and eleven 24s; total in the fort, sixty-two. Just outside of and below the main work, covering the approach to it, was a water battery carrying one X-inch and two VIII-inch columbiads, and two rifled 32-pounders.[4] Of the guns in Jackson, the flanking howitzers and half a dozen of the 24- and 32-pounders could, from their position, have had little or no share in the battle with the fleet.