For 150 years, the five original versions of Abraham Lincoln's famous Gettysburg Address have endured the ravages of time, but thanks to a team of committed scientists, with the exception of a few flaws, most of the documents remain in exceptionally good condition. It's no easy task keeping them that way: To protect them from the dangers of overexposure, when they are not being displayed, the artifacts are kept in the dark at cellar temperature and a humidity level of under 48%, with some versions kept in oxygen-free containers to protect them from light-induced oxidation.

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