Who found the treasure chest in the book Holes by Louis Sachar?

In the book "Holes" by Louis Sachar, the treasure chest is found by Stanley Yelnats. While digging at Camp Green Lake, he uncovers the chest alongside his friend Zero, after they dig in a spot where they believe the treasure might be buried. The chest contains valuable items that link back to the history of the Yelnats family and the story's overarching themes of fate and friendship.