Since the 1990s, the identifying label of "transfronterizos" has emerged in border scholarship to theorize the experiences of transborder, U.S.-Mexico border resident families and individuals. Transfronterizos have also been characterized as U.S. and Mexico cross-border residents with dual citizenship, who attend school, work, and forge families across nations. They have also been described as bilingual and bicultural people that possess tight affective ties on both sides of the border. While the existing border literature provides appropriately general and schematic understandings to theorize on the lives of cross-border families and individuals living on the Tijuana and San Diego border region, this dissertation centralizes the memories, voices, material realities, and lived experiences of "transborder citizens" themselves. To do so, this dissertation draws from oral history approaches and ethnographic research methodologies to excavate transborder citizens and families' past experiences and present lived realities in the Tijuana and San Diego border region. Based on my findings, I refer to "transborder citizens" instead as, fronteriza/os. This dissertation does three things. First, it historicizes the rise of transborder family units and transborder citizenship practices on the Tijuana border from 1889 to 1965. In the same vein, I also explore and theoretically advance the post-1965-1989 rise of "transborder parentocracy," an intentional and aspirational upwardly-mobile practice to give birth north of the borderline so that middle and upper-class border children can benefit from a U.S. birthright citizenship status in the Tijuana and San Diego region. Secondly, I theorize on the present-day and lived transborder family and citizenship experiences of fronteriza/os. I found that transborder family units also include members of mixed-legal status living at the U.S.-Mexico border. Thus, I further advance that fronteriza/os' articulate and construct a form of "transborder legal consciousness," shaped by U.S. citizenship and Mexican dual nationality laws. On the one hand, fronteriza/os' legal consciousness is implicated by a U.S. citizenship status that is shaped in relationship to family members mixed-legal status at the border. On the other hand, fronteriza/os' transborder legal consciousness is complicated by a limited and differential access to Mexican dual nationality. Third, and lastly, I theoretically encapsulate fronteriza/os' transborder family and citizenship experiences, including the construction of a transborder legal consciousness, through the border localized and aspirational "Tijuana Dream" narrative. I argue that ultimately, the notion of the "Tijuana Dream" is fueled by narratives of exceptionalism and meritocracy, promoting the idea that the "American Dream" is readily available to U.S. citizens and transborder families living at the Mexican border city of Tijuana. Through the exploration and theorization on the historical genealogies and quotidian social practices shaping transborder citizens' experiences in the Tijuana and San Diego border region, this dissertation fills a void at the intersection of Border Studies, Law and Society, and Chicana/o and Latina/o citizenship scholarship. This dissertation further expands the theories of transborder citizenship, legal consciousness and mixed-legal status families with the inclusion of "transborder mixed-status family" experiences, the practice of "transborder parentocracy," and the construction of a "transborder legal consciousness" into academic circles.