First-generation college students (i.e., those whose parents do not hold a bachelor's degree or higher), enter college without the same resources, skills, and knowledge as their non-first-generation counterparts which may lead to disadvantage regarding their chosen field of study in college (Prospero and Vohra-Gupta 2007; Roksa and Levey 2010; Wilbur and Roscigno 2016). Despite increases in their post-secondary participation, research has begun to highlight that first-generation college students are underrepresented in STEM fields (Chen and Carroll 2005; Chen and Soldner 2013; Ruder and Van Noy 2007). Because majoring in STEM can lead to important long-term outcomes for first-generation college students, understanding the factors that lead to STEM degree completion has implications for stratification within higher education and the U.S. labor market (Chen 2013; Melguzio and Wolniak 2012; Kim et al. 2015).Much of the literature on the intersection of first-generation status and STEM focuses on students' experiences during and after college (Weston 2019). Less clear are first-generation college students' pathways into and out of STEM fields over the course of their secondary and post-secondary careers. Examining first-generation college students' pathways into and out of STEM fields of study has important implications for understanding how they experience inequality in higher education and processes of social mobility (Beattie 2014; Dickson 2010). Additionally, most research on STEM persistence concludes when students report leaving a STEM major, without exploring the subsequent college majors they switch into. This dissertation research addresses this gap and by examining first-generation college students' high school STEM aspirations, STEM participation and persistence in college, and college major destinations of first-generation college students that exit STEM.Many researchers examining major choice and persistence have focused on STEM fields because the number of students prepared for entering and succeeding in these fields is well below the desired level as indicated by recent educational policy (Shaw and Barbuti 2010). A substantial literature on these earlier life course stages gives clues to the sources of gender differences in the selection of science-related majors. Within this literature, scholars focus on both gender differences in ability and gender differences in preferences (Morgan et al. 2013). The pipeline literature provides a useful starting point for understanding the gender gap in STEM fields and careers, but it focuses disproportionately on social processes that unfold in college, graduate school, and early careers (Morgan et al. 2013). This is surprising given that many interventions to promote STEM career exploration are designed for high school students (National Science Board 2007). To study how college major aspirations in college may change over the course of secondary and post-secondary education, Chapter 2 examines first-generation college students' high school intentions with special attention to STEM fields.To address gaps post-secondary in STEM fields of study by first-generation status and gender, Chapter 3 assesses: (1) whether first-generation women and men differ from their continuing-generation counterparts in choosing an initial college major in a STEM field; (2) whether first-generation college students in an initial STEM major are more likely than their more privileged counterparts to persist in college; (3) whether first-generation college students in an initial STEM major are more likely than their more privileged counterparts to persist in a STEM major. My attention to STEM participation and persistence in college by first-generation status highlights curricular pathways that contribute to restricted labor market outcomes. Moreover, my analyses highlight ongoing patterns of segregation in STEM fields by gender and social class background.Past studies on STEM participation are limited by ending observations of students at the point of departure from a STEM major, which is viewed as not persisting in STEM, or by only examining the major that a student obtains their degree in. The ability to track students' movements between various majors between matriculation and graduation represents one way to address these limitations (George-Jackson 2011). Previous research finds little difference by parental education in terms of the rate at which students left STEM majors for a non-STEM field (Chen 2013). However, other work finds evidence that students' subsequent pathways may reflect a patterned relationship to the STEM majors that they left and vary by students' academic performance and socioeconomic status (Weston 2019). The factors that contribute to first-generation college students' attrition from STEM may also influence their subsequent college major choices. In Chapter 4, I rely on literatures surrounding the factors that impact first-generation college students' decision leave STEM and examine the major choices of students that choose to leave STEM fields of study but persist in college. [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://www.proquest.com/en-US/products/dissertations/individuals.shtml.]