This article analyzes professional challenges to the 1915 commitment law and the ultimate demise of eugenic institutionalization in Illinois. It reveals the pivotal role of psychologists and intelligence testing in the debate over the necessity and viability of a state-sponsored system of eugenic commitment. It focuses primarily, but not exclusively, on a specific group of young female test subjects and the female professionals who attempted to measure their intelligence. The article relies on published studies as well as case records chosen at random from the Illinois State Training School for Girls at Geneva to explain and analyze the complex relationships among mental testing, feeblemindedness, and eugenics. Focusing on Geneva enables the author to highlight and evaluate previously underanalyzed social and environmental factors that affected testing as well as the experience of women in both eugenics and intelligence testing.