Complex sentence: Additionally, the 1959 opening of the Saint Lawrence Seaway also adversely affected the NYC freight business as container shipments could now be directly shipped to ports along the Great Lakes thus eliminating the railroads once lucrative freight hauls between the east and the midwest.
Split into simpler sentences: Additionally, the 1959 opening of the Saint Lawrence Seaway adversely affected the NYC freight business. Container shipments could now be directly shipped to ports along the Great Lakes, eliminating the railroads' once lucrative freight hauls between the east and the Midwest.