In the version of Lead Belly, the Midnight Special is a train “The Golden Gate Ltd, between Houston and San Francisco that on his way passes in front of the Texas State Prison in Sugarland, where Lead Belly was in prison..

In the version of Big Joe Turner it’s also a train, that, on a saturday, used to bring whores to well behave prisoners.
It was one of the most popular prisonsong in the south of the States, especially after a prisonrebellion in 1923 in Houston. The song in fact has to be much older, the copyright from Howard Odum dates from 1911.
Another prisonsong ‘If you ever go to Jackson”, uses the same melody.