Complex sentence: Before Pendleton retired she initiated many new buildings on the college grounds and created a $10 million endowment during her presidency; she was president of Wellesley College for 25 years.
Split into simpler sentences: Before Pendleton retired she instigated many new buildings on the college grounds and produced a $10 million endowment during her presidentcy. She was president of Wellesley College for 25 years.