This question is entirely based on an opinion, and this always makes me feel uneasy about a quiz question – no matter how commonly held that opinion may be. There's always a chance that the person answering the question has a different opinion.
Wikipedia would ask, "[Seen] by whom?"
I would suggest that such matters should always be put beyond argument by the inclusion of some indisputable fact. For an event such as this (a battle), a date should usually be enough: in this case, 1–3 July 1863. Or, in this particular case, you could mention that the US Soldiers' National Cemetery was dedicated on the site of the battle, later the same year.
To mention the famous address given by Abraham Lincoln, to mark the dedication of the cemetery, might be giving too much away.
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