Complex sentence: The Fort William Library saw its first major change when an addition was added to the south side of the building in 1955, increasing the floor area from 14,000 square feet to 23,150 square feet.
Split into simpler sentences: The Fort William Library saw its first major change when an addition was added to the south side of the building in 1955. The floor area was increased from 14,000 square feet to 23,150 square feet.