Colorado became the first state in recent years to revise its constitution in 2018 to ban slavery and involuntary servitude, followed by Utah and Nebraska in 2020.

Source: https://www.independent.co.uk/news/world/americas/us-politics/california-ap-nevada-sacramento-slavery-b2283264.html

Last year, voters in Vermont, Oregon, Tennessee and Alabama approved historic ballot measures that removed slavery and involuntary servitude as punishment for crime from their state constitutions, which could lead to limitations on forced prison labor.

Source: https://www.latimes.com/california/story/2023-02-27/california-involuntary-servitude-slavery-constitution-amendment-prisons

“Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States,” it reads.

Source: https://www.schwartzreport.net/2023/05/27/u-s-among-17-countries-that-practice-forced-labor-a-form-of-modern-slavery-report-finds/