At an unknown date, Mack had formed a business partnership with his cousin Merrill Elmaren Mack. He was incompetent, and when he died March 25, 1844, he left Stephen Mack with substantial debt and much useless merchandise. Mack abandoned trading and merchandise altogether and bought a dairy farm west of Rockton which was managed by the Stocker family (his second daughter Mary married Charles Stocker). As time passed and interest in his settlement dwindled, Mack bought up all the remaining available lots, and at the time of his death, all of the land which comprises the present Macktown Forest Preserve was owned by him.