Complex sentence: Mitchell was a member of the New York State Assembly (New York Co., 35th D.) in 1898; and a member of the New York State Senate (21st D.) in 1899 and 1900.
Split into simpler sentences: Mitchell was a member of the New York State Assembly (New York Co., 35th D.) in 1898. He was a member of the New York State Senate (21st D.) in 1899 and 1900.