Mestranol was discovered in 1956 and was introduced for medical use in 1957. It was the estrogen component in the first birth control pill. In 1969, mestranol was replaced by ethinylestradiol in most birth control pills, although mestranol continues to be used in a few birth control pills even today. Mestranol remains available only in a few countries, including the United States, United Kingdom, Japan, and Chile.