Recent case reports highlight the resurgence of rickets in certain groups of breastfed infants. Infants residing in the North, irrespective of skin color, and dark-skinned African American infants residing anywhere in the United States are most vulnerable to nutritional rickets if they are exclusively breastfed past age 6 months without vitamin D supplementation. At the turn of the 20th century, rickets was nearly universal among African American infants living in the North. The discovery of vitamin D, the initiation of public health campaigns to fortify infant foods with vitamin D, and the supplementation of vitamin D to breastfed infants were responsible for overcoming the rickets scourge. We review a classic nutritional study by Alfred F. Hess, one of the greatest clinical nutritional researchers of the early 20th century, in the context of the resurgence of rickets, especially among dark-skinned infants. The Columbus Hill district, a black community of New York, NY, served as the setting for the study. Sixty-five infants (aged 1-17 months) entered a 6-month open-label trial of daily cod liver oil therapy. Participants were assessed for signs of rickets at recruitment and at 2, 4, and 6 months. Cod liver oil prevented the development of rickets in 34 (92%) of 37 infants treated for 6 months and in 7 (58%) of 12 treated for 4 months. Of the 16 infants who did not take the prescribed treatment, rickets progressed unremittingly in 15. Hess translated his success into a public health campaign leading to the development of the first rickets clinic in 1917. This was the first step in the conquest of the rickets epidemic of the early 20th century.