Why did slavery end in the US?
Because the North won - having issued the Emacipation
Proclamation (chiefly to keep out the British, rather than for pure
Abolitionist sentiment), resulting in the liberation of many slaves
by the Union armies. It turned out to be a wartime measure that
could not have been rescinded afterwards.
The common misconception is that it ended (in the US) when Abraham
Lincoln Signed and approved the emancipation Proclamation.
This is, however, wrong. The Emancipation Proclamation only
officially ended slavery for slaves in "rebellious" states... i.e.
just those that denied that the government of which Lincoln was
president had any power over them.
It did have one immediate effect: the Union Army stopped
treating captured slaves as "contraband enemy property" and began
immediately freeing them. However, slavery didn't officially end in
the US as a whole until December 6, 1865, when Georgia ratified the
13th Amendment pushing it over the requirement of ratification by
at least 3/4 of the states and making it a part of the US
It also might be noted that while the 13th amendment freed
slaves in general, it expressly permits involuntary servitude as
punishment for crimes. Slavery in that sense is technically still
constitutional under US law, though it's since been abolished by
all states individually with the last being Alabama in 1927.
It is still endemic in many parts of the world.