I wonder if that one district in Southeast Louisiana in the 1860's was actually still represented in Washington during the War or if its just a mistake.
It is two districts actually.
In that era, congressional elections were spread out over two years. The 1st Congress met on March 4, 1789 and the originalists decided that meant that congressional and presidential terms would begin on that date.
This presented a problem for presidential elections, since electoral votes are counted by Congress, and if there were no majority, the House of Representatives would choose the president from among the top 5 candidates. At the time it was anticipated that this would be the norm.
In 1789, the 1st Congress did not have quorums on March 4, so couldn't meet to count the electoral votes. By the time they did get quorums, counted the votes, and determined that Washington had been elected, and for Washington to travel to New York City where Congress was meeting, it was June of 1789, three months into his term.
Congress determined that it would not be a good idea to have a presidential vacancy every four years, so they decided that the outgoing Congress would count the electoral votes, and if necessary the House would elect the president.
Congress is required under the Constitution to meet at least once per year, with a default of December. Because no one wanted to be in Washington in the summer prior to air conditioning, a winter schedule worked well.
So the schedule was like this:
March 4, odd year, beginning of term.
9 months: Cicadas.
December, odd year, beginning of first session,
Winter-Spring, even year, first session, until work was done.
December, even year, beginning of second session.
Winter (until March 3), odd year, conclusion of second session. If this was the beginning year of a presidential term, the electoral votes would be counted, and if necessary the House would elect the president. The Jefferson-Burr election, and the Adams-Jackson-Crawford election were in early 1801 and 1825, respectively, and there was pressure to determine a president before March 4.
The House is not a continuing body, so it was impossible to continue past March 3, and impractical to begin a new session on March 4, with a potentially wholesale turnover. The Senate is a continuing body, and in a very short session at the beginning of the first term of a new president would meet to consider the president's cabinet nominees. The Senate may only meet for a short period without permission of the House.
Congress would then go home.
If the 37th Congress wouldn't actually meet until December 1861, it didn't necessarily make sense to hold congressional elections in the fall of 1860. Those already in office would meet in Washington in December 1860, even if they had been defeated.
It wasn't until summer of 1861, that Lincoln decided to call a special session of Congress.
The use of odd-year congressional elections was quite prevalent in the South. Only Arkansas and Florida had congressional elections in 1860, and none of those elected served in the 37th Congress. Among border states, Missouri and Delaware had elections in 1860. Two of the Missouri representatives were expelled.
By the time most of the southern states would have held elections, the States had seceded. In eastern Tennessee, they were able to barely organize elections in three districts. One of the representative-elect was arrested and imprisoned on his way to Washington by the CSA, and another barely served at the end of the term.
The Wheeling government organized elections in the western portion of Virginia, and with the help of the USA military, in some areas opposite Washington.
New Orleans was occupied by USA troops in spring of 1862. There was apparently enough control to hold an election, in December 1862. The two representatives were seated in February 1863, about two weeks before the end of their term.
There were elections in five districts in Louisiana in 1864, but Congress never acted to decide whether to seat those elected.
