A major developmental task for young children in the United States involves the acquisition of knowledge about the letters in the English alphabet. In the current study, we examined the growth trajectories of children's letter name knowledge (LNK) during pre-kindergarten and kindergarten. A diverse sample of 1,015 children was drawn from the National Center for Early Development and Learning Multi-State Study of Pre-Kindergarten. Latent class growth analyses were used to identify three heterogeneous classes of children based on their LNK growth trajectories. Children's fall-of-pre-kindergarten language skills were associated with trajectory class membership, which in turn was associated with children's spring-of-kindergarten literacy skills. We also found that the association between children's fall-of-pre-kindergarten language skills and spring-of-kindergarten literacy skills was partially mediated by trajectory class membership. These findings point to the importance of LNK skill development as a marker variable to monitor and support children's emergent literacy development.