Brainerd worked at the Pan American Union from 1909 to 1935 and then Women's International League for Peace and Freedom's US section.
[1] After graduating from Smith College in 1904, she moved to Mexico City and worked as a secretary in a law firm and learned Spanish.
[2] On 22 June 1935, Brainerd retired from the Pan American Union[3] and was immediately recruited by the Women's International League for Peace and Freedom (WILPF) as a chair for the US Section.
She did not try to hide the fact that her previous employment at the Pan-American Union might cause raised-eyebrows and questions of imperialist motives, but addressed the issue and reassured the women in other WILPF branches of her sincerity.
[4] Her efforts in Mexico for the most part did not succeed, as though there was initial progress[5] by the mid-1930s it was clear that for Mexican women the fight for political rights was not the same as the internationalist's goals.