A Free Air Concentration Enrichment (FACE) experiment was established in one of the world’s most productive soybean growing areas in Central Illinois in 2001. This facility (SoyFACE) allows investigation of the response of field-grown soybean to an atmosphere predicted for 2050 without alteration of the microclimate. While improvements in carbon assimilation and water use efficiency led to increases in maximum leaf area index (LAI) in elevated [CO₂], the molecular drivers of increased LAI in elevated [CO₂] are unknown. The first objective of this research was to investigate transcript changes in growing and fully expanded soybean leaves grown in elevated [CO₂]. The second objective was to identify transcripts involved in leaf growth and elongation, and to investigate how elevated [CO₂] altered the expression of those transcripts. We used cDNA microarrays to identify 327 transcripts that showed a significant change in expression in elevated [CO₂], including transcripts involved in sugar transport, glycolysis, and carbohydrate metabolism. 1146 transcripts showed a significant change in expression in growing vs. fully expanded leaves. These genes were largely involved in protein synthesis and RNA processing.  We further identified 139 transcripts with a significant [CO₂] by development interaction response, which included transcripts involved in amino acid metabolism, hormone metabolism, and lipid metabolism.  This work provides novel insight into changes at the transcript level that are involved in leaf growth responses to elevated [CO₂].