America. This action was supposed to show that Lincoln was still in charge of the entire United States. The Civil War was the bloodiest war fought inside the United States. 620,000 were killed and millions more were injured. One of the bloodiest battles of the Civil War was the Battle of Gettysburg in Pennsylvania. 51,000 people from both sides died, more than in any other battle. The Civil War ended in 1865 when General Robert E. Lee of the Confederate Army surrendered.