Complex sentence: The lake was formed in 1908 behind a multiple-arch dam, which was part of a large lumber operation, at first called the Kings River Lumber Company (Johnston, 34), which ceased production in 1917, due to a major fire.
Split into simpler sentences: The lake was formed in 1908 behind a multiple-arch dam, which was part of a large lumber operation, run by a company at first called the Kings River Lumber Company (Johnston, 34). That company ceased production in 1917, due to a major fire.