Which was NOT a Union state?

The majority of slaves in the USA were Africans. Slavery in the United States was abolished in 1865 with the 13th Amendment to the U.S. Constitution. Today, slavery is illegal in most countries. Abraham Lincoln was President during the time of the abolition of slavery in the USA. In the mid-19th century conflict grew between the northern and southern states over the issue of slavery, leading to a long and bitter civil war.