Answer:
During his presidency, the most significant events was most definitely the Civil War that ended in 1865 with the North and the South parts of the United States.
Step-by-step explanation:
To give a brief introduction, Abraham Lincoln was the 16th President of the United States, serving from March 1861 until his assassination in April 1865. Lincoln led the United States through its Civil War—its bloodiest war and its greatest moral, constitutional and political crisis.
If he was president of a country during such a moment of chaos, you might wonder: How was Abraham Lincoln viewed throughout the civil war?
Larry Tagg wrote a great book that examines the media coverage of Lincoln during his administration, in great detail. The paperback edition is titled “The Battles that Made Abraham Lincoln”, with a clunky subtitle. The original title of the hardback edition was “The Unpopular Mr Lincoln”, which is much punchier and makes more sense. I recommend this book very highly, in either edition, to get a flavor. Remember that journalism was a lot rougher and rawer then, than it is today: less genteel, fewer protocols about objectivity and sources and ombudsmen etc etc.
Lincoln was holding onto a very fractious coalition. Basically all sides hated him. Abolitionists were impatient because he was a gradualist and said outright that he would accept slavery if it would restore the Union. Copperheads were against him because he went to war against the Southern states. There was just no way to reconcile the various elements in the North; and of course the South wanted him dead. (And eventually got that.)
MacLellan hated him because Lincoln was his boss. Chief Justice Taney of SCOTUS hated him because he disregarded Taney’s writ of Habeas Corpus for Merryman. Newspapermen hated him because his soldiers shut down some papers; or just because he didn’t do what they expected. The Maryland legislature hated him because he arrested a third of them. Modern Lost Cause devotees hate him because he won the war.
He seems to have been pretty popular among the Northern electorate; and of course among soldiers. Everyone else had a beef of one kind or another. Lincoln did his job anyway, and let the chips fall.