[citation needed] It was based in Harlem in Upper Manhattan, New York City, around 125th Street, in what was then a predominantly Jewish neighborhood.

The Lenox Avenue Gang was started in the early 1900s by Horowitz as an independent group of around twenty members.

Mainly operating around 125th Street in Harlem, then a predominantly Jewish neighborhood, the gang generally committed muggings and robberies, but Zelig occasionally hired them for murder.

Under Horowitz's leadership, the gang produced many of the top criminals of the early century, including Jacob Seidenschner, Louis Rosenberg, and Francesco Cirofici.

Gyp the Blood, Jacob Seidenschner, Lefty Louis Rosenberg, and Francesco Cirofici were charged with the murder of Rosenthal.