James was born May 26, 1928 in Embarass, Wisconsin to John Mackowiak and Wihelimina Dillenburg. He had a twin brother, John.
In 1930, they were residing in Belle Plains, Wisconsin.
James married Dorothy Peeters on May 19, 1954 at St. Mary's Catholic Church. James and Dorothy had eight children. Dorothy had a younger sister, Helen, who married James' twin, John.
James and John farmed together until 1959, when John bought his own farm.