If the emancipation proclamation only freed southern slaves, when did northern slaves become free

The declaration of Independence founded the roots of abolishing slavery in the North. Vermont became the first to ban slavery in its 1777 state constitution. It is reported that by 1804 all the states in the North had voted in favor of banning the slavery within their boundaries. While on 22 September 1862 Abraham Lincoln issued his preliminary Emancipation Proclamation.

is that it?

explanation:

we have pictures for proff

they also have books