The Carolina County Ball is a fictional event (there is no Carolina County), but it sounds like a rocking good time. For young bands, getting these gigs can be a big deal, and in this song, lead singer Ronnie James Dio assumes the role of upstart musician who can't wait to get on stage and play.
According to the Roy Davies biography Rainbow Rising: The Story Of Ritchie Blackmore's Rainbow, "Carolina County Ball" was released as a single on Purple Records. Roger Glover produced it, along with the eponymous album; he also sang backing vocals on it.
"Carolina County Ball" was actually the B-side of "L.A. 59," which was released in Germany as a test pressing on April 8, 1974. Running to 4 minutes 45 seconds, it was co-written by frontman Ronnie Dio and keyboard player Mickey Lee Soule.
Suggestion credit: Alexander Baron - London, England, for above 2