1950 DDT shown to disrupt sexual development in roosters, and “may exert an estrogen-like action.”
Burlington H, Lindeman VF. Effect of DDT on Testes and Secondary Sex Characters of White Leghorn Cockerels. Proceedings of the Society for Experimental Biology and Medicine. 1950;74(1):48-51.
1953 DES sales peaked, then declined after it was shown to be ineffective to prevent miscarriage in a controlled, randomized, double-blind study. “Even so, DES continued to be prescribed during pregnancy until 1971, in large part because pharmaceutical companies discredited the study and heavily promoted DES to doctors.”
Dieckmann, W.J. , Davis, M. E., Rynkiewicz, L. M., and Pottinger, R. E. (1953). Does the administration of diethylstilbestrol during pregnancy have therapeutic value? American journal of obstetrics and gynecology, 66(5), 1062–1081.
Source: DES Action timeline