The purpose of this study was to examine the development of English reading achievement among English Language Learners (ELLs) and to determine whether the time that an ELL's family was in the United States and the type of native language spoken affected their reading development. Participants were 300 third-grade ELLs from two different native language backgrounds (93 Somali-speaking and 207 Spanish-speaking students) who attended a large Midwestern urban school district. Students' reading achievement was assessed using curriculum-based measurement and a statewide reading assessment. Moderated multiple regression and multiple-group latent growth curve analyses were conducted. Results indicated that the time an ELL's family had been in the U.S. was an important factor in understanding the development of ELLs' reading achievement, whereas language type did not appear to be as important. Implications for research and practice associated with understanding and promoting English reading development among ELLs are discussed. (Contains 4 tables.)