The Peirce-Welby correspondence has been an invaluable source for the historians of logic and semiotics mapping the development of Peirce's thought and of the significs movement. The unpublished Peirce-Ladd-Franklin correspondence provides equally important insights into the development of theories of logic and meaning, science and reasoning, and language and intelligence. Taking Ladd-Franklin's contributions into account puts the received historiography on modern logic, semiotics, pragmatism, and linguistic philosophy in a new light. She was also a pioneer in women's rights in higher education and scientific research.