The Scottish County Football League was one of several supplementary football leagues that were created in the early days of competitive football in Scotland in order to increase the number of fixtures for Scottish Football League clubs.
The only season in which it is known that this competition definitely took place is 1899–1900, and the only information available is that the championship was shared by Abercorn and Ayr and that the other members included Raith Rovers, Hamilton Academical, Motherwell & East Stirlingshire.
References
Scottish County Football League Wikipedia(Text) CC BY-SA