Complex sentence: By 1875, Clarksburg was a major town in the northern part of the county, but the construction of the Baltimore and Ohio Railroad undermined its economy, and by the late 20th century Clarksburg was barely a shell of its former self.
Split into simpler sentences: By 1875, Clarksburg was a major town in the northern part of the county, but the construction of the Baltimore and Ohio Railroad undermined its economy. By the late 20th century Clarksburg was barely a shell of its former self.