This project aims to address the critical shortage and low retention of STEM secondary teachers in U.S. schools, thus helping to address an important national need. Additionally, the project aims to help overcome current opportunity gaps in STEM experiences on the Arizona-Mexico border. The project will support the collaboration of experienced, skilled STEM teachers with scientists and science educators to develop educational field stations at environmental reclamation sites. These field stations are expected to provide opportunities for field trips and experiential learning. Thus, they have the potential to ignite a STEM spark in the majority Latino border communities and increase public knowledge about science. A local science center will collaborate with the project to design and develop the field stations. Societal benefits of this project include advancing student potential in a region characterized by poverty, English language learner populations, low educational achievement levels, and a lack of STEM opportunities outside of school. This project at the University of Arizona will include strategic partnerships between the Rural Activation and Innovation Network (NSF #1612555), Cochise County School District, Bisbee Science Exploration and Research Center, Freeport McMoRan Industries, and Cochise County Engineering, Natural Resources Division. Project goals are to provide experienced, exemplary STEM teachers with opportunities to build their leadership skills in three core areas: field-based instructional materials design, coaching, and collaboration. A total of 14 exemplary multi-disciplinary STEM teachers will be selected as Master Teaching Fellows for this six-year project. The project addresses knowledge gaps in informal STEM for rural communities and builds on the knowledge base about teacher collaboration. The project tests the potential for improving STEM education through development and use of teacher-designed field stations as teaching sites for STEM subjects. It focuses on rural border areas that lack opportunities for informal STEM learning. In addition, it gives Master Teaching Fellows the training and support to become classroom coaches and to lead a professional learning community, providing teachers the opportunity to design and lead teacher development efforts in an underserved border area. Project evaluation will use a mixed-methods approach including front-end, formative, and summative evaluation phases. Dissemination plans include research publications and conference presentations, a Sin Fronteras website that Master Teaching Fellows will design and maintain, and local media coverage. This Track 3: Master Teaching Fellowships project is supported through the Robert Noyce Teacher Scholarship Program (Noyce). The Noyce program supports talented STEM undergraduate majors and professionals to become effective K-12 STEM teachers and experienced, exemplary K-12 STEM teachers to become STEM master teachers in high-need school districts. It also supports research on the persistence, retention and effectiveness of K-12 STEM teachers in high-need school district. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.