This is concise thumbnail summation by the historians at the National Park Service concerning the second day of fighting during the Battle of Gettysburg:
"By the afternoon of July 2, the powerful forces of Meade and Lee were at hand, and battle on a tremendous scale was imminent. That part of the Union line extending diagonally across the valley between Seminary and Cemetery Ridges held. Late in the forenoon, General Dan Sickles, commanding the Third Corps which lay north of Little Round Top, sent Berdan's sharpshooters and some of the men of the 3rd Maine Regiment forward from Emmitsburg Road to Pitzer's Woods... as they reached the woods, a strong Confederate force fired upon them..."
As a result of of the heavy fighting at Little Round Top, Devil's Den, Culp's Hill and the Peach Orchard - July 2nd clocked-in as the bloodiest day during the whole of the battle, with over 15,000 killed or wounded.
It was on the first day at Gettysburg that the Confederates made a terrible mistake. Read about it here.
Click here to read about the events of the third day during the Battle of Gettysburg.