Human milk, widely understood to be beneficial for infants, can be lifesaving for preterm neonates, especially in reducing the risk of necrotizing enterocolitis. Donor human milk (DHM) is an option when mothers are unable to provide milk or have an inadequate supply for their infants. Nonprofit donor human milk banks are established to provide safe, processed human milk from milk donated by healthy lactating mothers who have undergone a rigorous screening process. These milk banks, operating under the auspices of the Human Milk Banking Association of North America, obtain, process, and dispense human milk under strict guidelines set by the association. Increasing the supply of donor human milk to meet a dramatic increase in demand poses a significant challenge for nonprofit milk banks. Efforts to increase supply nationwide include education of providers, use of social media to engage potential donors, and outreach to news media. In parallel, milk banks are establishing regional depots to collect donations, and additional milk banks are being developed. This article describes the current nonprofit milk bank industry in the United States, its challenges, and its future prospects.