This study investigates first-generation and non-first-generation engineering undergraduates' math/science identities, subject-related interests, and career plans. First-generation students are an understudied, but growing population. Understanding how these self-beliefs and background factors affect students' engineering choice can help widen pathways into engineering which continues to be defined as 'pale and male.' Additionally, identity has predictive value for practical outcomes like engineering choice in college. The data for this study comes from the nationally representative Sustainability and Gender in Engineering (SaGE) survey completed by 6,772 college students who enrolled in first-year English courses at 2- and 4-year colleges across the U.S. Data were analyzed using t-test and chi-square tests for linear and dichotomous outcomes respectively. Our results show differences in first-generation students' identities, interests, performance/ competence beliefs, and family support for science. These differences can serve as a stepping stone towards understanding the trajectories of first-generation college students in engineering. By understanding underrepresented students' identities, performance, and backgrounds, specific strategies can be developed to support these students in our engineering programs.