Lathrap left California in 1959, taking a post at the Department of Anthropology at the University of Illinois at Champaign-Urbana, where he significantly influenced the department's archaeological direction. He worked in South American archaeology, which focused on the Amazon and Peru.
Lathrap's move from California in 1959 led him to the University of Illinois at Champaign-Urbana's Department of Anthropology, where he played a crucial role in shaping its archaeological agenda. His research expertise was centered on South American archaeology, with a specific focus on the Amazon and Peru.