Malmbanan
Born in Wyk auf Föhr as the youngest son of O. C. Hammer, Hammer was the first in his family to get Swedish citizenship when he moved to Gällö in Jämtland in 1885. Hammer was a trained engineer and helped his father with the expansion of the Gällö sawmill. He moved to Norway in 1899, where he worked as a Swedish Consul and as the French General Agent for the Narvik Iron Ore Line.