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.