Complex sentence: The Scottish Football League was established in 1890, initially as an amateur league until professionalism in Scottish football was legalised in 1893, the same year in which a Second Division was formed, with the existing single division renamed the First Division.
Split into simpler sentences: The Scottish Football League was established in 1890, initially as an amateur league until professionalism in Scottish football was legalised in 1893. In 1893 a Second Division was formed, with the existing single division renamed the First Division.