This dataset documents the phenotypes of 617 maize genotypes grown in the absence (“mock”) and presence of 10 mM indole-3-acetic acid (IAA) in .tif image format. This large-scale seedling data, which contains images in different 18 folders, increases our understanding of the phenotypic ranges displayed by maize in numerous agriculturally relevant traits, including organ size and responses to a key growth regulator.