Excellent question, I'll try to give you a throrough answer. The Civil War was fought from 1861-1865 and pitted the US Government and the Northern States against the Confederate States the "South" that had left the Union in the wake of Abraham Lincoln's election as President in 1860. Lincoln and his party were swept into power promising that no more slave states would be added to the Union. The South knew that if they could not keep up with the non-slave-holding North in the U.S. Senate, then they would be powerless and at the mercy of Northern interests. The South was led by President Jefferson Davis, a Mississippi Senator, West Point graduate, and hero of the Battle of Buena Vista during the Mexican War. Southern military heroes include: Generals Robert E. Lee, Thomas Jonathan "Stonewall" Jackson, A.P. Hill, and J.E.B. Stuart. The North, led by Lincoln had several future U.S. presidents in the Army like Ulysses S. Grant, Rutherford B. Hayes, James Garfield, Benjamin Harrison and William Mckinley. Other Northern military leaders were Generals William T. Sherman, Phillip Sheridan and George Armstrong Custer.
Major battles raged from Pennsylvania all the way to the Mississippi River and included huge Southern victories like Bull Run, Fredericksburg, Chacellorsville, Chickamauga, Cold Harbor, etc.
Some Northern victories were: Gettysburg, Vicksburg, Chatanooga, Shiloh, and the seige of Atlanta.
The bloodiest day of the war was at Antietam, in Maryland, which was a tactical draw. But Lincoln called it a victory and used it to announce his "Emancipation Proclamation" freeing all of the slaves in the states that were still rebelling against the United States government on Jan. 1, 1863.
By 1865, Northern manpower and industrial superiority finally wore down the south and Robert E Lee surrendered to Grant in April at Appomatox, Virginia, and Joseph E. Johnston surrendered to Sherman a short time later in North Carolina. They were the two biggest Southern armies in the field and it meant the war was essentially over, although sporadic fighting went on for a short while. Licoln didn't see the complete victory, he was assassinated in April, of 1865, days after Lee surrendered. Davis, was captured and kept in prison (but was never tried for a crime) and then release. He wrote a history of the Confederacy and died in Louisiana in, I think 1889.
It was the bloodiest war in American history with over 630,000 dead and more than 1 million total casualties in a nation much smaller than today.