A renowned architect known for his innovative designs, married to Catherine, whose affair with Mamah Bouton Borthwick challenges societal norms and personal relationships.

Mamah's husband at the start of the novel, a kind man whose simple pleasures contrast with Mamah's desire for intellectual stimulation and connection with Frank.

Mamah's living sister, a supportive yet eventually strained family member who grapples with the public scrutiny brought on by Mamah's decisions.

Frank's first wife, who becomes a symbol of societal expectations and challenges Mamah and Frank's relationship by refusing to grant a divorce.

A Swedish philosopher and suffragist whose writings inspire Mamah, especially in matters of love and marriage, and whom Mamah translates, despite some controversies surrounding her views.