This dissertation examines Theodore Roosevelt’s second daughter Ethel Roosevelt Derby. One of the main aims of this dissertation is to contribute to the field by constituting a case study of Ethel Roosevelt Derby, relying on a vast corpus of primary and secondary sources. While doing this, the dissertation concentrates on some prominent aspects of Ethel Roosevelt Derby’s biographical sketches in order to scrutinize how Theodore Roosevelt’s daughter becomes “the Roosevelt child,” who espouses the legacy of her father. In this regard, how her father Theodore Roosevelt and his ideals regarding the strenuous life, conservationism, progressive vision of the government and the nation, and social-community service for the good of society, shaped Ethel Roosevelt Derby’s life is the central point of this dissertation. The most noteworthy characteristic Ethel Roosevelt Derby shared with her father is her fervent commitment to caring for others and serving the community. As a Roosevelt, Ethel preserved the virtue of participating at any kind of benevolence for the good of the public, of the country, and, without doubt, of humanity in general. In that vein, through Theodore Roosevelt’s daughter’s life, this dissertation will shed light on the concepts of noblesse oblige, philanthropy, humanitarianism, and voluntary action for the public good in the twentieth century American history, and the role of the philanthropic voluntary associations on the lives of the Roosevelts, focusing mainly Theodore Roosevelt’s father Theodore Roosevelt Sr., Theodore Roosevelt himself, and his daughter Ethel Roosevelt Derby.