New York Tribune article, May 8, 1862.

Federal troops captured the city  on this day during the Civil War. The
the looting of the Post Office in the Custom House is related in the below
editorial from the "Evening True Delta" published in New Orleans, Louisiana,
issue of May 8, 1862

Vandalism. It was only yesterday evening that we were informed of the
disgraceful acts of the mob that, for a time, had their saturnalia in and around
the new Custom-house building, on the evening of the day that the Federal forces
took possession of that building. The facts laid before us - and we are
satisfied they are unquestionable - are these: The Federal forces took
possession of the Custom-house, Postoffice, etc. At sundown of that day the
Federal force was ordered to return to the fleet at anchor opposite the city.
When they left, the rowdies broke open the doors of the Postoffice, and for a
time, had a perfect saturnalia in that establishment. They took possession of
everything but the vault, which they could not enter; they took all the letters
they could lay their hands on, and, we presume, rifled them of their contents;
they carried off a valuable gold watch, the private property of the postmaster,
and a large amount of specie, and, in fact robbed and plundered the
establishment...

The partially completed Custom House was first
occupied in 1856 when the U. S. Customs Service moved into the first floor. The
Post Office moved into the Custom House in November 1860, and the building
served as the city's main post office through the remainder of the nineteenth
century.

Standing as a major symbol of the Federal Government, the
unfinished Custom House  played a significant role during the War Between
the States. In 1861 the exterior masonry walls were complete up to their full
height, while the interior masonry was still incomplete. Although construction
was suspended, the building was occupied briefly by Confederate forces and then
by the Federal Army after New Orleans was captured in 1862. The notorious Union
General Benjamin Butler established his headquarters on the second floor in the
offices that face Canal Street. The building was also used to house captured
Confederate soldiers, reportedly up to two thousand men at one time.