On May 30, Illinois became the 37th state to pass the Equal Right Amendment (ERA), which says, Equality of rights under the law shall not be denied or abridged by the United States or by any State on account of sex." Next, advocates aim to secure the final state needed to ratify the amendment. They will probably target Virginia, North Carolina or Georgia. The law is overdue. Many Americans assume that the United States already has gender-equality rules. The Civil Rights Act, Title IX and the Equal Pay Act all offer protections against discrimination. But these are pieces of legislation. New laws and Supreme Court rulings can diminish their power. An amendment, by contrast, would force a constitutional reckoning for sex-based discrimination. Activists lobbied, marched, went on strike and persuaded Congress to pass the amendment in 1972. Within just two years, 34 states ratified it. Then the momentum faltered. The amendment failed to secure ratification from the four additional states needed before 1982, the expiration date set by Congress. Passing the ERA will not be easy. Fierce opposition has long accompanied feminist surges, and this is already happening today. In Illinois, Republicans largely spoke out against the amendment. The dominant party could block the ERA's path at the federal level, and other states could rescind their decades-old ratification. Securing the final state to pass the ERA will probably prove as challenging as it was to secure the final state to pass the 19th Amendment a century ago.