<p>STEM education has been a topic of reform in education for many years and it has recently focused primarily on the education methodology called STEM integration. Universities and state departments of education have defined teacher education programs and STEM initiatives that explore the necessary ingredients for a curriculum using this methodology, but they do not provide explicit instructions for the design of the learning environment. The purpose of this study was to explore the question "What are the characteristics of high school learning environments that support integrated STEM instruction?" </p> <p>This qualitative study used a postpositive lens and multiple-case study framework to distill the experiences and evidence gathered from four STEM certified high schools in the state of Indiana. This distillation resulted in three universal themes common to each school which were: the allocation of universally accessible free space for STEM integration, the importance for mobility of resources and students, and the need for supportive technological resources. </p> <p>This study is applicable to both those who are educators working in STEM education and those researchers looking to understand the STEM integration paradigm or learning environment design. Educators can use this study to plan their own learning environments and researchers can use this study as a pilot to many other outlets in the topic of STEM integration. </p>