What do you feel the most important election of US history is?

[True Federalist (진정한 연방 주의자)]

1860 is objectively the correct answer. No other electoral contest has so fully and irrevocably decided the national character.

No that's 1800. 1860 had the most important nominating convention as who the Republicans chose would have a major impact, but the South acting like spoiled brats was inevitable that year.

[True Federalist (진정한 연방 주의자)]

I think the standard should be 'how much would history have diverged had the other guy won' as well as how close it was. 1860 is an obvious answer; I'd also make a case for 1912 and 1936, given their potential impact on US involvement in the world wars, as well as long-term social and economic policy.

1912 didn't have that much effect. If Teddy had been President, the Lusitania incident, if it still happened, would have gotten us involved sooner, but while that would have increased Allied manpower, it wouldn't have significantly increased Allied war materiel as 1915-6 was the period we ramped up war production anyway. Maybe a year gets shaved off the length of the war and the Bolsheviks don't take power.

[True Federalist (진정한 연방 주의자)]

1860 is objectively the correct answer. No other electoral contest has so fully and irrevocably decided the national character.

No that's 1800. 1860 had the most important nominating convention as who the Republicans chose would have a major impact, but the South acting like spoiled brats was inevitable that year.

Is not that nominating convention a part of the election? It's beyond dispute that the South was going to try and break off from the Union in 1861 no matter what.

That assumes that the Republicans win the White House in 1860.  Assume for the moment that Democrats either hadn't had their 2/3 rule or Douglas manages to get nominated in Charleston despite it. The result is a Douglas victory:

Alternatively, assume that Bell isn't kept off the New York ballot, allowing him to split off some of the ex-Whig vote that Lincoln got, handing the State to Douglas:

There are a few other scenarios that lead to the election going to Congress, but the essential thing is that the Senate was solidly Democratic, so given a choice between the running mates of Lincoln and Breckenridge, it would undoubtedly pick Lane over Hamlin.  That leaves the Republicans with the choice of either supporting Douglas in the House or leaving the Presidency vacant because the House was unable to elect a President with an ardently pro-slavery Vice President serving as Acting President.

Roll Call of the States: U.S. House Election for President in 1860 (36th Congress):

I'm uncertain how Tennessee and Delaware would have voted, but I'm fairly certain that Texas and California would have both been split 1-1 between Douglas and Breckenridge.  This assumes of course that the Republicans accept a Douglas presidency as the lesser of two evils, If they don't, then Lane serves as Acting President until at least December 1861 when the 37th Congress takes office.

[True Federalist (진정한 연방 주의자)]

Why don't anyone think 2016 election is significant in history?

There's no evidence so far that Trump's election has fundamentally changed our political system in any respect.