The purpose of "The Pathways and Experiences of Illinois Computer Science Undergraduate Students Series," as the name suggests, is to understand the pathways and experiences of computer science (CS) and tech students in post-secondary programs throughout Illinois, paying particular attention to students from historically marginalized groups including Black/African American and Hispanic/Latinx students, women, first-generation students, and low-income students. The series will include several reports, each focusing on a different aspect of students' experiences or pathways into and through CS education. This first report of the series focuses on the specific supports that helped students succeed and barriers that may have impeded their success in their post-secondary CS education programs.