On March 22, 1972, the Equal Rights Amendment is passed by the U.S. Senate and sent to the states for ratification.

First proposed by the National Woman’s political party in 1923, the Equal Rights Amendment was to provide for the legal equality of the sexes and prohibit discrimination on the basis of sex. More than four decades later, the revival of feminism in the late 1960s spurred its introduction into Congress. Under the leadership of U.S. Representative Bella Abzug of New York and feminists Betty Friedan and Gloria Steinem, it won the requisite two-thirds vote from the U.S. House of Representatives in October 1971. In March 1972, it was approved by the U.S. Senate and sent to the states.

READ MORE: Why the Fight Over the Equal Rights Amendment Has Lasted Nearly a Century

Hawaii was the first state to ratify what would have been the 27th Amendment, followed by some 30 other states within a year. However, during the mid-1970s, a conservative backlash against feminism eroded support for the Equal Rights Amendment, which ultimately failed to achieve ratification by the a requisite 38, or three-fourths, of the states, by the deadline set by Congress.