Complex sentence: Lamar would go on to represent Mississippi in the United States Senate from 1877 to 1885 and served as United States Secretary of the Interior under President Grover Cleveland from March 6,1885 to January 10,1888.
Split into simpler sentences: Lamar would go on to represent Mississippi in the United States Senate from 1877 to 1885. Lamar served as United States Secretary of the Interior under President Grover Cleveland from March 6,1885 to January 10,1888.