Abraham Lincoln at the signing of the Emancipation Proclamation, which gave slaves their freedom.
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Updated: June 30, 2017 1:55 PM ET | Originally published: June 30, 2017 10:30 AM EDT

In the roughly two and a half centuries since America first celebrated its independence, there have been plenty of opportunities for moments big and small to sway the course of the nation’s history.

That’s why, to mark the Fourth of July holiday, TIME History asked 25 experts to pick one such moment. It could have happened on a day that every American child learns about in school — the day Abraham Lincoln spoke at Gettysburg, for example — or it could have happened on a day that might otherwise blend into the rush of history. Big or small, however, it had to have made its mark.

In past years, we’ve looked at such moments in the 20th century — you can see those lists here and here — but this year we’re going back in time even more, to the 19th century. The only rules were that the selections had to be specific moments (so that means “the Civil War” doesn’t work) and they had to have happened between Jan. 1, 1800, and Dec. 31, 1899. The results, contributed by email and phone, highlight 25 days out of the hundreds that passed during that century and, in doing so, trace the nation’s evolution from infancy to modernity.

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