In 1903, the National Police Gazette wrote that Irish boxers were received by audiences with "a hearty cheer and earnest backing." For a time in the United States, the Irishman became the idealized boxer; the apotheosis of masculinity. The "Emperors of Masculinity," as author Gerard Earley described the leading heavyweight boxers of the era, had become Emerald Emperors. This book is the first in depth study of the role played by Irish and Irish Americans in the sport of boxing in the United States. It examines the lives of many men who contributed to the sports' development and looks at their stories through social, cultural and historical lenses. It is a story of assimilation and how some Irish and Irish Americans achieved their dream and others fell by the wayside through the most brutal sport of all.