Born in Bloomington, McLean County, Illinois, Brennan attended parochial schools. He was employed as a reporter for the Bloomington Bulletin. He was graduated from the Illinois Wesleyan University in Bloomington, Illinois, in 1902.
Born in Bloomington, McLean County, Illinois, Brennan attended Catholic schools. He was employed as a reporter for the Bloomington Bulletin. He graduated from the Illinois Wesleyan University in Bloomington, Illinois, in 1902.