The Emancipation Proclamation largely applied to slaves in areas that were not yet under Union control and that gives people the opportunity to argue that the Proclamation was toothless or ineffective. There will always be a group of people who want to take a contrary position for the sake of being disagreeable.
But, yes, Lincoln began the process of freeing the slaves with the Emancipation Proclamation. It’s not as if the Proclamation was rolled back or swept under the rug once those rebellious regions came under Union control. More importantly, the Proclamation gave slaves an understanding that they had a ticket to freedom declared by the President of the United States. Scores upon scores of slaves were encouraged by word and proof of the Proclamation and gave them genuine hope and belief that their government would back them up if they took the step of breaking their own chains of bondage and heading North or finding their way into Union military lines. Without that sense of legal protection, it seemed almost unthinkable for most slaves and their families to set out on their own. It did not free every slave in every region of the United States, but it was a green light (forgive the anachronism) to leave the horrors of human bondage behind in order to take the long walk to freedom.
Incidentally, the Emancipation Proclamation had an very important impact on the Union soldiers, too. With the Proclamation, President Lincoln made it crystal clear that the Civil War was no longer just an attempt to crush a rebellion and hold the United States together. From that point forward, the abolition of slavery officially became a leading aim of the war. Earlier during the Civil War, President Lincoln famously wrote to the New York Tribune’s Horace Greeley:
"My paramount object in this struggle is to save the Union, and is not either to save or to destroy slavery. If I could save the Union without freeing any slave I would do it, and if I could save it by freeing all the slaves I would do it; and if I could save it by freeing some and leaving others alone I would do that."
The Emancipation Proclamation was a declaration that the “paramount object” of the struggle for Lincoln (and, through him, the entire Union military) had shifted and abolishing slavery was now the leading mission of the Union war effort as Northern troops began turning the tide and claiming some much needed battlefield successes. Whether or not it immediately applied to their region on January 1, 1863 when the Emancipation Proclamation went into effect, it had a tangible impact on slaves throughout the country as an obvious first step in the progression from human bondage to the landmark Thirteenth Amendment to the Constitution, which officially abolished slavery in the United States of America.
First of all, Lincoln did NOT own slaves. Not ever.
Secondly, people have argued for nearly 150 years about whether Lincoln did or did not free the slaves and whether the Emancipation Proclamation was toothless or actually had some juice behind it. It’s popular to say that Lincoln didn’t free the slaves and it is certainly arguable, but really, he kinda did. A war to preserve the Union eventually became a war to end slavery in the United States and that was a decision largely made and stuck to by Abraham Lincoln. People can and will argue and argue and argue about that point, but let’s look at it in a totally simplistic way: Slavery existed before Lincoln became President and began prosecuting the Civil War, but by the time of Lincoln’s assassination slavery basically ended with the Emancipation Proclamation, 13th Amendment, and surrender of General Lee to General Grant at Appomattox. Did Lincoln free the slaves by himself? No, but his idea of victory in the Civil War shifted considerably throughout his Administration from preservation to emancipation.
So, yeah, he kinda did.
The Emancipation Proclamation was largely symbolic. It freed the slaves in most of the areas under rebellion, not throughout the entire country, and almost all of the places covered under the order were controlled by the Confederacy at the time of its signing.
What it really did is signify that the Civil War was being fought for more than the suppression of a rebellion or the preservation of the Union. The Emancipation Proclamation made it clear that the abolition of slavery was a key objective in the war. With the Emancipation Proclamation, Abraham Lincoln basically married himself to emancipation as a condition of victory.
It doesn’t matter that the actual order was virtually toothless. The symbolism behind the Emancipation Proclamation helped lift the spirits of an oppressed people, helped establish a lofty cause for a nation exhausted by combat, and ensured that foreign countries would resist supporting or giving international recognition to the Southern Confederacy because of the North’s intention to abolish slavery.