Complex sentence: USS "Ethan Allen" (1859) was a 556-ton bark acquired by the Union Navy during the beginning of the American Civil War, and used as a gunboat in support of the blockade of Confederate waterways.
Split into simpler sentences: USS "Ethan Allen" (1859) was a 556-ton bark acquired by the Union Navy during the beginning of the American Civil War. She was used by the Union Navy as a gunboat in support of the Union blockade of Confederate waterways.