Eastman is considered to be one of the last of the 19th-century New York City gangsters who preceded the rise of Arnold Rothstein and the Jewish mob.

According to the 1880 United States Census, 5-year-old Edward Eastman lived with his mother and other family on East Seventy-Fifth Street, in Manhattan.

In the 1860 census, Samuel Eastman was living as a single man in Manhattan in the household of Thomas McSpedon, from a prominent old NYC family.

His mentor's firm, McSpedon & Baker, on Pine Street in New York, was the official printer for the city government.

In addition to running his business, McSpedon served as an elected Alderman in NYC and as appointed City Fire Marshall during the mid-19th century.

By the 1900 census, Mary Eastman lived in Queens on Curtis Avenue, with her daughters Elizabeth and Francine and their families.

[3] At some point, he returned to live on the Lower East Side and became involved with the neighborhood gangs made up of poor, young men, often children of immigrants.

Because his criminal enterprise involved so many members of Jewish-American organized crime, Eastman is frequently depicted as being Jewish (including by some newspapers of his period).

In time, Monk's reputation as a tough guy earned him the job of "sheriff" or bouncer at the New Irving Hall, a celebrated club on Broome Street, not far from his pet shop.

Eastman's greatest rival was Paul Kelly (born Paolo Antonio Vaccarelli), an immigrant leader of the majority-Italian Five Points Gang.

The warfare between these two gangs reached a fever pitch on September 17, 1903, with a protracted gun battle on Rivington Street among dozens of gangsters.

[10][11][12] Tammany Hall worked closely with both Kelly and Eastman to mobilize their members in elections and patronage schemes.

Its officials grew tired of the feuding and the bad press generated when civilians were killed or injured in the gangs' cross-fire.

In 1903, Tammany Hall set up a boxing match between Eastman and Kelly in an old barn in the Bronx to settle the feuding.

During his military physical, the doctor observed all the knife and bullet scars on Eastman's body and asked him which wars he had been in.