The Emancipation Proclamation (Proclamation 95) only gave freedom to slaves who were enslaved in territories hostile to the Union and after they made their way past the Union forces. It did not free any slaves who were enslaved in the Union nor territories that were neutral.
By the summer of 1862, the Union forces had dwindling numbers due to the deaths and low recruitment numbers. In addition to this problem, there was a growing population of enslaved people who had escaped their slave masters in the south that they did not know what to do with. These escapees had limited ability to make a living. In an effort to remedy both of these situations, Proclamation 95 was proposed. By the end of the war, over 200,000 escaped slaves were declared free with Proclamation 95 and joined the Union army.