HEATHSVILLE, Va. (AP) — State officials in Virginia are unveiling a historical marker that honors a man who freed more than 500 slaves.

The Virginia Department of Historic Resources says the marker honoring Robert Carter III will be unveiled Saturday in Heathsville in front of the Northumberland County Courthouse. The marker notes that on Sept. 5, 1791, Carter filed a document, called a “deed of manumission,” at the courthouse. The document eventually freed more than 500 slaves that Carter owned in several Virginia counties. Carter wrote that to keep the men and women enslaved “is contrary to the true principles of Religion & Justice.”

Carter’s deed liberated slaves gradually in small groups. Children were freed when they reached adulthood.