Complex sentence: In 1965 a new wing of upper floor galleries was added to the building's west wing, and the following year, the Clarence B. Hanson, Jr. Library was opened on the building's first floor.
Split into simpler sentences: In 1965 a new wing of upper floor galleries was added to the building's west wing. The following year the Clarence B. Hanson, Jr. Library was opened on the building's first floor.