“In the 1880s, women began in large numbers to supplement their own milk with cows’ milk shortly after giving birth and to wean their babies from the breast before they were 3 months old.
This represented a stark change from the colonial era, when mothers normally breastfed at least through infants’ second summer. The move to early weaning was so relentless that doctors complained bitterly in a 1912 issue of the Journal of the American Medical Association that breastfeeding duration rates had been declining steadily since the mid-19th century ‘and now it is largely a question as to whether the mother will nurse her baby at all’.”
from: Wolf JH: Low breastfeeding rates and public health in the United States. Am J Public Health. 2003 Dec;93(12):2000-10. (full-text)