IIRC, there's 2 that do that explicitly - I want to say it was Texas and North Carolina, but I can't be bothered to double check that.
Edit: was bothered by my lack of "bringing the reciepts" in my own comment. It appears 5 of the confederate States called out slavery in their articles of succession (tried to do a quick double check, but jfc did GA have a really long winded one and I ain't got time for that right now)
Not sure if I should up vote to raise awareness or down vote to disagree with intended policy.