At the Battle of Shiloh....it is known as the bloodiest battle for both sides of both the Union and Confederacy.
Days
April 6, 1862 through April 7, 1862
Death Toll for Confederacy
Dead - 1,723
Missing - 959
Death toll for Union
Dead - 1,754
Missing - 2,885
The battle of Shiloh took place in Tennessee NOT Pennsylvania
About 10,000 casualties on the Union side (the exact number is 13047), with 10699 on the confederate side. It was a Union tactical victory, but the Union lost more men.