You can roam the battlefield as much as you want for free, but the NPS charges 5.50 (with a AAA discount) for a very pedestrian historic house museum. Most of the exhibits in the house were almost instantly forgotten -- the bedroom exhibit aside.
To be honest, I was disappointed overall with downtown Gettysburg. I don't know what I was expecting exactly, but the area fell short. A better museum/visitors' center would help.
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