For nearly all infants, breastfeeding is the best source of nutrition and immunologic protection, and it provides remarkable health benefits to mothers as well. Many mothers in the United States want to breastfeed, and most try. Yet within only three months after giving birth, more than two thirds of breastfeeding mothers have already begun using formula. By six months postpartum, more than half of mothers have given up on breastfeeding. This Call to Action describes specific steps people can take to participate in a society-wide approach to support mothers and babies who are breastfeeding. It provides recommendations for women and families, communities, health care providers, employers, public health agencies, and researchers.