Little is known about 2nd language development among young, low-income, language-minority children. This article examined the longitudinal English development of low-income, dual language learners (DLLs) in Miami ("n" = 18,532) from kindergarten through 5th grade. Growth curve modeling indicated that social skills, good behavior, Spanish (L1) competence in preschool, having a mother born in the United States, and attending larger schools with fewer DLLs were associated with higher initial levels of English proficiency in kindergarten and/or steeper growth over time. Survival analyses indicated that it took about 2 years for half of the sample to become proficient in English according to the school district's criterion. Higher initial proficiency in kindergarten, not receiving free/reduced lunch, not being Hispanic or Black, strong cognitive, language, and socioemotional skills at age 4, and maternal education were associated with faster attainment of English proficiency. It is important for teachers, parents, researchers, and policy makers to understand that DLL students come from diverse backgrounds and that poverty and other factors influence the speed of English language development for DLLs.