Spatial reasoning skills are a great predictor of students' Science, Technology, Engineering, and Mathematics (STEM) achievement and attainment. However, researchers have mainly viewed spatial reasoning skills as an internal cognitive process that is measured through the administration of psychometric testing and laboratory experiments. Further, while spatial reasoning is focal in shaping one's thinking and learning in an engineering context, there is a lack of understanding of how and when spatial thinking is useful in K-12 engineering classrooms. This dissertation extends the current understanding of spatial thinking by examining how various cognitive resources and material resources are utilized, discussed, and enacted by elementary school students and their instructors to support one's engagement in spatial reasoning. The current study collected data from a three-week summer learning program, with one week dedicated to engineering units. During the space and aviation week of the summer program, students worked collaboratively in groups of two to four students to create two Alka-Seltzer rocket ships. The researcher chose a collaborative learning environment for the study to observe how spatial reasoning processes occur in the context of social interaction. The study utilizes an interaction analysis method to analyze moment-by-moment social interaction and object representations that took place in student-to-student and students-to-teacher interactions. This study provides a qualitative account that examines spatial reasoning in naturalistic social interaction to extend the understanding of how spatial reasoning is useful in K-12 engineering education. In addition, this dissertation provides an understanding of how various material resources are effective in cultivating various spatial reasoning processes. The results of the study showcase ten different spatial cognitive processes that are observable through social interactions. Students and teachers utilized a plethora of spatial cognitive processes throughout the engineering unit and at varying stages of the engineering design process. The study demonstrates that, as the activity progressed, students' engagement in spatial cognitive processes shifted. Complex challenges that arose during the engineering activity pushed students to come up with creative solutions by calling upon a wide array of spatial cognitive processes. While the timeframe of the activity was short, the study was able to demonstrate nuanced development in students' spatial reasoning through social interaction. Finally, while engaging in spatial cognitive processes, students also drew upon various material resources to assist them. The study found that different materials possess unique spatial properties and elicit different types of spatial cognitive processes. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]