OK, the premise of it being "celebrated annually on June 19 to commemorate the end of slavery in the United States" is plain off wrong.
There were two documents "ending" slavery: The Emancipation Declaration of 1863 and the Thirteenth Amendment.
Slavery in the United States was officially abolished with the ratification of the Thirteenth Amendment on December 6, 1865. However, the Emancipation Proclamation issued by President Lincoln on January 1, 1863, declared freedom for slaves in Confederate states, but did not end slavery nationwide.
On September 22, 1862, President Lincoln issued his Preliminary Emancipation Proclamation, which stated that enslaved people in those states or parts of states still in rebellion as of January 1, 1863, would be declared free. One hundred days later, with the rebellion unabated, President issued the Emancipation Proclamation declaring "that all persons held as slaves" within the rebellious areas "are, and henceforward shall be free."
In the slave-owning areas controlled by Union forces on January 1, 1863, state action was used to abolish slavery. The exceptions were Kentucky, Delaware and New Jersey [1], where chattel slavery and indentured servitude were finally ended by the Thirteenth Amendment in December 1865.
“The Emancipation Proclamation did not lead to widespread freedom of African Americans,” says Berry. “It didn’t change that many people’s lives. Very few enslaved people were given their freedom after the Emancipation Proclamation.” --Time Magazine,When Did Slavery Really End in the U.S.? The Complicated History of JuneteenthThe Thirteenth Amendment:
Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.
So, the Emancipation Declaration of 1863 freed slaves in Confederate states but did not apply to border states or areas under Union control. That meant that slavery was still practised in Kentucky, Delaware, and New Jersey up until 6 December 1865.
Juneteenth was not in any way the end of slavery in the United States.
That's because the Thirteenth Amendment, which was passed on 6 December 1865 officially abolished slavery in the U.S.
The Emancipation Proclamation only applied to the states which were active members of the Confederate States of America. I couldn't get an accurate number on the amount of enslaved people in Delaware, Kentucky, and New Jersey at the time of the 13th Amendment, but I would guess it was more than heard General Order #3 in Galveston, Texas on "Juneteenth".
The final nail in the coffin for this nonsense is:
But even when slavery did end in Texas, formerly enslaved people still had a long road to freedom ahead of them, as they faced inadequate infrastructure to support them as they started new lives. As Laura Smalley, who was born into slavery in Texas, recalled that bittersweet moment in a 1941 interview, “We didn’t know where to go. They turned us out just like, you know, you turn out cattle.”
Even more cold water: Furthermore, thousands of black slaves were not freed until after the Reconstruction Treaties of late 1866, when the Cherokee, Creek, Chickasaw, Choctaw, and Seminole tribes were forced to sign new treaties that required them to free their slaves.
So much for Juneteenth ending slavery in the United States.
Footnote: there were 16 people enslaved in New Jersey when the 13th Amendment was passed!



