[1] Her women's bookbinding union became a branch of the American Federation of Labor (AFL) and she went on to become a full-salaried organizer.

[3] Her union organization became a part of the AFL and as a result she was elected to delegate to the Chicago Trades and Labor Assembly.

[2] In the year after she was terminated Kenney would continue to work in labor organization, particularly with Florence Kelley.

Throughout their marriage O'Sullivan continued her organizing mostly through the settlement house, holding discussion groups for working women, focused on the need for solidarity.

[4] From these discussions came the beginnings of an organization that would provide working women from varied backgrounds a central voice, enabling them to unite for better wages and conditions.

Labor leader and President of AFL Samuel Gompers allowed her time at the microphone to announce the founding of the National Women's Trade Union League (WTUL).

The first meeting included women from many previously established unions, as well as settlement house leaders and reformists.

Initially the WTUL was able to offer support, opening a relief station providing strikers with survival goods, O'Sullivan was made the operator.

The Industrial Workers of the World (IWW), a rival union organization which held opposing viewpoints, supported the strike.

She thought that IWW's policy of including diverse ethnic and craft divisions would "lead to that 'spirit of confidence'".

[10] After O'Sullivan finished her relief work with the Lawrence Strike she went on to get legislation passed that would improve the conditions in Massachusetts's factories.

[2] She was hired in 1914 by the state as the inspector for the Massachusetts Board of Labor and Industries, a position which gave her the power to enforce the laws she helped pass.

In 1999 a series of six tall marble panels with a bronze bust in each was added to the Massachusetts State House; the busts are of O'Sullivan, Florence Luscomb, Dorothea Dix, Josephine St. Pierre Ruffin, Sarah Parker Remond, and Lucy Stone.