Alpena’s greatest fire occurred July 12, 1872, when about fifteen acres were laid to waste, and upward of $175,000 worth of property destroyed. The number of buildings destroyed was not far from seventy. The heart of the city was destroyed, and scarcely a store remained on the south side of the river. But the people met the emergency with manful energy, and fine brick blocks were erected on the sites of the wooden buildings burned.
Source : History of Alpena County, pp. 234-235.
For more information about early Alpena, see The Town That Wouldn’t Die ; Alpena, Michigan By Robert E. Haltiner