In 1862, when Karns murdered thirteen prostitutes, he used his hook as his weapon. After Karns' execution, the hook was returned to St. Barnabas Church along with all of Karns' other worldly possessions. The hook was melted down and reforged into an unknown number of silver objects kept in the church.
After becoming a violent spirit, Karns' hook remained his murder weapon in the afterlife. When hunters Sam and Dean Winchester investigated Karns' latest series of attacks, they learned about the history of the hook. Due to the hook being a part of Karns', the hook in its reforged forms kept Karns' ghost tied to the Earth even after Dean salted and burned Karns' bones.
To end Jacob Karns for good, the Winchesters gathered every silver object in St. Barnabas Church and melted them down in the church furnace. The effort initially failed with the ghostly version of Karns' hook injuring Sam in the arm before the Winchesters realized that Lori Sorensen's necklace was part of the hook. After Dean melted the necklace, the hook was effectively destroyed and with it, the ghost of Jacob Karns.