SPOILER ALERT!!!!
Read no further if you don't want a hint for Challenge 3!
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Go to our library's Baltimore Sun database.
When you're in the database, in the top search box, type:
Battle of Antietam
Click Search.
When you get the search results, on the left, use the "Sort by" menu to choose "Oldest first."
Then your results will rearrange themselves, with the September 18, 1862, article about the Battle of Antietam at the top!