Henry Darcy was a distinguished engineer, scientist, and citizen who is remembered for his many contributions in hydraulics, including Darcy's law for flow in porous media. While he has been given full credit for the finding, little insight has been available on the process of his discovery. It is shown that his discovery was the logical result of a lifetime of education, professional practice, and research. Darcy understood both its significance and its relationship to the broader fields of hydraulics and groundwater hydrology. Besides the discovery of Darcy's law, he was the first to show that significant flow resistance occurs within aquifers, the first to recognize the law's similarity to Poiseuille flow, and the first to combine the law with continuity to obtain a solution for unsteady flow.