Complex sentence: A shipbuilding boom in the early part of the 20th century became massive during World War I, making Seattle somewhat of a company town; the subsequent retrenchment led to the Seattle General Strike of 1919, the first general strike in the country.
Split into simpler sentences: A shipbuilding boom in the early part of the 20th century became massive during World War I, making Seattle somewhat of a company town. The subsequent retrenchment led to the Seattle General Strike of 1919, the first general strike in the country.