Teachers play a critical role in the preparation of future science, technology, engineering, and mathematics majors and professionals. What teachers know about their discipline (i.e., content knowledge) has been identified as an important aspect of instructional effectiveness; however, studies have not yet assessed the content knowledge of aspiring chemistry teachers in the United States. The Praxis Chemistry Subject Assessment is the most nationally representative measure of teacher content knowledge, used in 39 U.S. states in the past decade. In the presented study, we report findings concerning (i) the demographics of Praxis Chemistry Subject Assessment examinees (i.e., prospective chemistry teachers); and (ii) the longitudinal trends in exam performance across several demographic test-taker characteristics. These findings reveal substantial differences in performance and pass rates among examinees of different genders, races/ethnicities, undergraduate majors, undergraduate GPAs, and geographic locales in which they intend to teach. We establish potential leaks in the teacher pipeline that may impact the quality and diversity of chemistry teachers in the United States and suggest ways to improve the chemistry teaching workforce.