It's really "House of the Rising Sun," but it's called "In New Orleans" on the old 78 (Musicraft, I think, without looking it up) and on all the LP/CD reissues of it. I had this on a Sutton LP from the 60s, the first Leadbelly record I ever owned, purchased for 77 cents out of a bargain bin at G C Murphys. ("Leadbelly Sings Songs of Bad Men and Beautiful Women, with the Satin Strings," 8 tracks in all.)

The thread at the top of the page, "Leadbelly Chords," contains several posts about the song, including a good description of the guitar part by Steve-O.

Tab for the song is in Julius Lester's "12-String Guitar as Played by Leadbelly," an Oak book from the 60s, but NB that he only tabs the first half of the guitar break. The second half is the same, except for the last two or three notes -- easy to work out if you know the first half, as it just resolves back to the tonic, where the first half ends on the dominant.

It's in G but the progression is slightly unusual, and the bass runs are what make it.