Research in the past millennium gave us formidable advances in the fields of Cu nutrition, biochemistry, animal and human health. Insights into Cu‐Fe interactions highlighted much significant advancement. The recognition that Cu was an essential mineral for Fe metabolism and hemoglobin biosynthesis traces back to a paper by Hart et al. at Wisconsin appearing in the first third of the century. This observation came at a time when the only known function of Cu was that of a constituent of hemocyanin pigment in some mollusks and crustacea. The Wisconsin group's studies were preceded by McHargue's work, which introduced glass‐lined cages to study trace mineral function, and in so doing, provided the first experimental evidence for Mn, Cu, and Zn essentiality. Here, we review the details of the experiments by Hart et al. that led to the discovery of copper's interconnection with Fe and important papers that have since given mechanistic clarity to the interaction. J. Trace Elem. Exp. Med. 14:207–210, 2001.