Mullen was born on June 11, 1847 During the 1820s and 1830s, John's father Denis and uncle Thomas Mullen, "crafted barrels for the mills" of Ballinasloe, which had three oatmeal mills, two breweries, and a flour mill. The Mullen family left Ireland during the Irish Potato Famine, also called the
Great Famine. They were among a wave of 1.2 million refugees who emigrated to the United States during the nine-year period from the year of Mullen's birth until 1856, when the family emigrated to the United States. The Mullens settled at
Oriskany Falls, Oneida County, New York, where Denis and Thomas purchased houses adjacent to each other, and close to the town mill. John Mullen dropped out of school and worked at age fourteen at the Oriskany Flour Mill. By the age of twenty he managed the mill. ==Businessman==