Teacher education programs have long sought to increase preservice teachers' competency through coursework that promotes content, pedagogical knowledge, and specialized forms of knowledge that interweave the two. Still, newly licensed teachers are entering K-12 institutions ill-equipped to provide mathematics instruction that is both impactful and meaningful. This problem has persisted consistently throughout elementary education as teacher candidates enter the classroom without the conceptual knowledge to teach mathematics effectively (National Research Council, 2003; Ryan & Williams, 2007; Stacey, et al., 2001). This dissertation aims to understand what standards and frameworks are available for teacher educators to utilize in the planning of their instruction, how teacher education programs in the primary grades are structured, and what elementary professors believe to be key concepts and tasks in the development of teacher candidates. From this information, along with a quantitative study that explicated teacher effectiveness from the various public institutions in this particular state in elementary mathematics, a case study was conducted to understand how one particular professor was developing teacher candidates. Based on this research, a conceptual framework was developed to illustrate what content, pedagogical content knowledge, instructional tasks and best practices this professor utilizes throughout her teaching. This conceptual framework illustrates the idea of developing teacher candidates knowledge of an overarching mathematical concept to allow application of this knowledge to other singular units of mathematical content and pedagogical knowledge. This new approach of developing threshold concepts opens mathematics education to overarching key concepts in elementary teacher education, or what is referred to throughout this dissertation as threshold concepts. These threshold concepts connect singular units of curriculum to a larger, overarching concept, that once internalized, would allow teacher candidates the ability for effective application of these concepts.