He emigrated to the United States, sometime before 1881, where he took up residence in the portion of New York's Lower East Side known as Klein Deutschland (little Germany).

Eventually he developed a real estate and insurance business as a broker and investor, building a successful firm, S. Steingut Company, first on Second Avenue, later at 47 West 42 Street, Manhattan.

The move was in fact away from his father and involved the turbulent relations between his parents, which resulted in their eventual divorce amid much ridicule in the press.

After Lena Woldach gave birth to Irwin, Simon obtained a modification of the decree from Judge Miles Beach.

Steingut agreed but objected to the allegations of cruelty, telling all that his wife (at six feet, almost 14 inches taller than him) regularly beat him.

[8] Four months later, just as he was about to fulfill his promise by marrying an "actress" with "a position at the Metropolitan Opera," he learned that a divorced wife still had a dower interest in any real estate he purchased.

Irwin was reluctant to follow his father's political career and after graduating law school became a reporter for Associated Press.

After a year working in journalism, Irwin entered his father's real estate and insurance business on Forty-Second Street, which became S. Steingut & Son.

[17] Simon Steingut's role as "Mayor of Second Avenue" was as one of 35 to 40 ethnic community leaders on the Lower East Side of Manhattan, who provided liaisons between government (and other institutions and persons of influence) and insular ethnic groups, usually made up of new immigrants or first generation Americans too ignorant or timid to deal with authority.

[19] In 1915 Simon was convicted of unauthorized practice of law at the beginning of a major sweep, in which "hundreds" of unlicensed lawyers were under surveillance.

[20] The services these little mayors undertook ranged from explaining government, legal or business usages to constituents to intervening with institutions like banks to providing holiday food or winter coal for the poor.

[10] But Tammany was above such petty squabbles, and Steingut was back in its good graces and rewarded with the commission for acquiring property for a new theatre to be built on Second Avenue between Fourteenth and Twenty-Third Streets.

[24] When Simon arrived at Hirschorn's, dressed in silk hat and morning clothes on June 4, Levy was ready to argue that Steingut was forfeiting his "office" by so long an absence.

The crowd suggested that Irwin Steingut be elected temporary mayor, and in the ensuing voting he bested Levy by a 44-vote majority.

In 1912, Simon Steingut collected a group of Jewish bankers and realtors to form a corporation (in which Big Tim Sullivan also had an interest) for the construction of a building on Second Avenue for two theaters as well as offices, lofts and a place for a dramatic school, for the production of Yiddish and German drama.

[26] Irwin's association with his father now got him noticed by both the press (the Tribune, for example, noted his presence at the following year's election by calling him a "slick young feller"[27]) and Tammany (at the large funeral of the Republican leader of the 8th Assembly District, Irwin was mentioned between Thomas H. Smith, secretary of Tammany and Samuel Gompers[28]).

[31] His break with the style of his father seemed complete when he began his campaign to have 1,000 businesses raise $50,000 to combat "radicalism" on the Lower East Side.

[34] The introduction proved the most fortuitous event in Steingut's life, for McCooey became his mentor, sponsor, and eventually closest friend.

McCooey was a self-made man, having taken on the role of head of a family (of a widow and six children) at the age of 13 when his father died in an accident.

Although he mastered all aspects of the service and was promoted to a more lucrative postmaster position, he was cashiered for political reasons when the Republicans regained control.

[35] He threw in with the local Brooklyn Democratic organization (for which he had been acting as a district leader) and obtained a post as deputy treasurer of King's County.

Through his association with Patrick H. McCarren, he obtained the position as secretary of the Civil Service Commission (located in Manhattan) in the new consolidated City of New York.

[39] Before Steingut's arrival, notwithstanding the efforts of the Madison Club, Democrats were rarely successful in sending a representative to Albany.

At the beginning of his career Steingut was not heard on the big issues—those that affected Brooklyn and the city and Democratic political generally, all of which were matters for the machine.

[50] By the end of the first term, with an eye toward re-election, Steingut made a play for popularity by championing the interests of boxing fans.

He called for a cap on ticket prices to bouts[d] and demanded an investigation into one of Harry Wills's fights to determine if it was "set up,"[53] He won re-election in November 1922 by a wide margin (53.5% to his Republican rival's 33%).

[57] Steingut also introduced a bill which called for an investigation into aeronautic stunts above populated areas and provided funds for legislative remedy.

[58] Steingut also proposed one of five Democratic bills seeking to increase compensation to certain New York City officials—proposals which Republicans dismissed as "a raid on the treasury.

On June 10, over 1,500 Democrats, practically all of the Madison Club membership and more, together with John McCooey, senator Jimmy Walker and paint magnate Arthur S. Somers as toastmaster, turned out for a dinner at Brighton Beach designed to create a "boom" for Steingut-for-Congress.

[66] The boom failed to gain momentum, and McCooey eventually endorsed Andrew L. Somers, Arthur's son,[67] in the Democratic primary.