Gettysburg is famous for its civil war history. It is the place where the bloodiest battle of this war took place. On july 1-3 1863 the CSA and Union army clashed. The battle left 51,112 death (23,049 Union and 28,063 Confederate) This is nearly 1 in 3, as 157,000 engaged in the battle.
The battlefield is a national park now and there are over 1000 monuments to commemorate this tragedy. Some are just plaques, but othes are regular pieces of art.
There is a selfguided auto tour leaving from the visitorcenter.
Battlefield Tour. It will take a full day, at least, but it is well worth the time. The serenity of the park gives no indication of the carnage that took place there.
The park is well maintained, and important sites are well-marked. The monuments are very moving
There are historic sites within the town but I've only had time to see the battlefield. It takes at least two hours but probably allowing four or five would help you be more thorough.