premise: The American Civil War took place in the 20th century.
hypothesis: The American Civil War was fought in the United States from 1861 to 1865 . After a long standing controversy over slavery and state 's rights , war broke out in April 1861 , when Confederates attacked Fort Sumter in South Carolina , shortly after Abraham Lincoln was elected . Four years of intense combat left 620,000 to 750,000 soldiers dead , a higher number than the number of American military deaths in World War I and World War II combined , and much of the South 's infrastructure was destroyed . The Reconstruction Era ( 1863 -- 1877 ) overlapped and followed the war , with the process of restoring national unity , strengthening the national government , and granting civil rights to freed slaves throughout the country .