In 1905, Baldwin joined with Frances Kellor, a social worker and attorney, to form the National League for the Protection of Colored Women in order to protect women migrating to the north who might be "easy targets for con men who could lead them into prostitution".

[6] She founded the Committee on Urban Conditions Among Negros with George Edmund Haynes in 1910.

"The business of the College, transacted in the presence of a mind so clear and sympathies so ardent, undergoes a change," wrote a colleague at Smith.

"To express at all what Mrs. Baldwin is and what she has given Smith College would require more space and more art than the present writer has at her command.

Ruth Standish Baldwin and George Haynes are honored as founders of the National Urban League with a plaque on the Extra Mile Path in Washington, D.C.[20]