It is well known that women are underrepresented in science. technology engineering and mathematics (STEM) and that their interest declines more steeply over the schooling years. As such, this study uses a STEM identity theoretical framework to examine the effects of early STEM experiences, focusing particularly on experiences that may be more formative for female students. Given that early experiences are a form of capital, the study is also guided by nuanced perspectives on STEM capital and STEM identity capital. The data used were drawn from surveys administered to 15,725 college students. Blocked regression models were utilized and the results indicated a significant effect on STEM identity for students who reported encouragement in STEM from elementary school teachers, using STEM toys/kits, watching STEM-related TV programs or movies, playing STEM computer/video games, and observing or studying stars and other astronomical objects. Negative experiences included baking/cooking/kitchen chemistry and writing about STEM. To examine which of these experiences had long-lasting impact in the face of intervening experiences in middle/high school, controls were provided for middle/high school STEM interest. This indicated early experiences that translated to STEM identity capital in the future. Only observing stars became nonsignificant, while the other early experiences likely contributed to STEM identity capital. The findings highlight early experiences that can be formative for STEM identity years later (i.e., STEM identity capital) despite intervening years of changing STEM interest. As such, the results provide both practical and theoretical insight into understanding the development and maintenance of STEM identity.