Little Round Top
One of the most popular and significant locations on the Gettysburg Battlefield, Little Round Top (the smaller of two large hills at the southern end of the Union line) saw fierce fighting on the second day of the battle. Little Round Top marked the left flank of the Union line along Cemetery Ridge, and its high ground oversaw the Wheatfield, Devil's Den and the area between Cemetery and Seminary ridges. But despite its importance, Little Round Top was largely left undefended early on the second day when Gen. Dan Sickles, against Gen. Meade's orders, advanced his units to the Peach Orchard to be closer to the Confederate lines (Sickles defended his move for the rest of his life, and if you contacted him today in a seance, he'd still insist he was right).
After being sent by Meade to explore the situation, Brig. Gen. Gouverneur K. Warren (depicted in one of the statues at the summit) found only a signal corps station and quickly summoned whatever units staff officers could reach to defend the area. Units from New York, Michigan, Pennsylvania and Maine formed on Little Round Top, with the 20th Maine defending the extreme left flank of the Union line.