Career
Born in Germany, Kretlow emigrated with his family and settled in Milwaukee, Wisconsin. Kretlow went to Spencer Business School and worked in the cigar making business with his father. In 1866, he moved to Wausau, Wisconsin where he was assistant register of deeds for Marathon County, Wisconsin.
He moved to Chicago, Illinois, in 1869, where he was again in the cigar making business.
Kretlow moved back to Wausau, Wisconsin. He was a bookkeeper and owned an abstract business.
He was elected Wausau City Clerk and then Register of Deeds for Marathon County. Kretlow was a Democrat.
In 1915, Kretlow served in the Wisconsin State Assembly.