Archaeobotanical samples from the Lamb site (11SC24) provide an opportunity to examine early Eveland phase (A.D. 1100–1150) plant subsistence in the central Illinois River valley (CIRV). We discuss the range of plant resources exploited by the Lamb site residents as well as seasonality and site occupation. We also consider the role of maize in Eveland phase subsistence economies. The Lamb site archaeobotanical data indicate the rapid adoption of maize in the Eveland phase CIRV, although site residents continued to rely on a diverse array of native plant taxa.