...an attempt was made by a small squadron of British ships stationed off the mouths of the Mississippi for the purpose of blockade to ascend the river. On the 9th of January, when opposite to Fort St Philip, they opened upon it a heavy fire of shot and shells, which, with few and short pause,s was continued for nine days and nights; when failing to make any impression favorable to themselves, on either the fort or the garrison, they withdrew to their former position. [Source]
From the National Park Service:
"Jackson had called attention to the importance of supplying New Orleans with some means of defense during September of the previous year, but after having prevented the British from finding a lodgement at Pensacola and Mobile he had now to face the fact that nothing had been done by the government at Washington to fortify the place.
As a main part of the defense, two effective batteries mounted with 24-pounders were located on the side of the river opposite Fort St. Philip, one at old Fort Bourbon and the other a half mile below. These were to operate in conjunction with the fire from Fort St. Philip."
|Across The Mississippi River From Fort St. Philip (Fort Jackson built AFTER the War of 1812)|
From the First Division Museum at Cantigny, a description of the battle as well as an oil painting depicting it; and from Wikipedia, the siege of Fort St. Philip.