1. ""jail" system - Pulaski"

Does anyone know how the "jail" system "worked" around 1880?
The 1880 Census Mound City Precinct lists a Wm McCoy as jailor.
Also living there were his wife, 2 brothers-in-law, a boarder and
3 prisoners.  What was this?  A "jail" farm?
Would this have been a certain building?  Did they have several of these?  And what exactly were "they"?
Also around that time, did Pulaski County have fairgrounds?

-----------------------------------------------------------------------------------------------------------------------------------------------------------------