Complex sentence: Formed in the fall of 1998, the band mainly performed in the Colorado-Illinois area, expanding their touring region to across the country, and even abroad by the summer of 2003, when they visited Europe.
Split into simpler sentences: Formed in the fall of 1998, the band performed mainly in the Colorado-Illinois area. They expanded their touring region to across the country, and by the summer of 2003 they visited Europe.