A SOCIALIST WRITER and thinker, Morris Hillquit was significant in defining socialism and the labor movement in the United States. Born as Moses Hilkowitz in Riga, Latvia, then part of Russia, he immigrated to the United States in 1886 when he was 17. He settled on New York's Lower East Side, a hotbed of immigrant radicalism. By day he worked in the garment industry and by night he participated in political discussions in English, Russian, and Yiddish on the Cherry Street rooftops. His interest in left-wing politics and labor unionism led him to establish the United Hebrew Trades, a Jewish garment workers' union, and to work with the well-established Socialist Labor Party (SLP).

He entered New York University in 1891, graduated in two years, and in ...