In 1915, Abraham Flexner delivered his lecture to the US National Conference of Charities and Corrections entitled ‘Is social work a profession?’ His conclusion to this question was (paraphrased) 'not yet', because social workers was a "mediator" not a "professional agent", and because social work was too broad in its scope. This was a key moment in the professionalisation of social work; from here on, educators and practitioners from both sides of the Atlantic sought to upgrade social work to make it a profession. Mary Richmond's subsequent book, Social Diagnosis, published in 1917, tried to refute Flexner by laying claim to the notion that casework was a technique that was unique to social work - it might therefore provide the answer to social work's need for its own distinctive knowledge and skills.
it should be noted that not all those at the conference were critical of social work. Porter Lee, chair of the New York School of Philanthropy stressed social work's expertise as promoting social welfare in ways that no other profession could or did. At the same time, Felix Frankfurter, a Harvard Law professor, urged that social work should become established with universities, arguing that, "These schools need the university. But the university also needs the school for social work" (Frankfurter 1915: 596, quoted in Jennissen and Lundy, 2011).
For more on this, read the entry for the first National Conference in 1874.
Also Jennissen, T. and Lundy, C. (2011) One Hundred Years of Social Work. A History of the Profession in English Canada 1900-2000, Wilfred Laurier University Press, Waterloo, Ontario.