Megan's Law was inspired by the case of seven-year-old Megan Kanka, a New Jersey girl who was raped and killed by a known child molester who moved across the street from the family. The Kanka family fought to have local communities warned about sex offenders in the area. The New Jersey legislature passed Megan's Law in 1994.
In 1996, the U.S. Congress passed Megan's Law as an amendment to the Jacob Wetterling Crimes Against Children's Act. It required every state to develop some procedure for notifying the public when a sex offender is released into their community. Different states have different procedures for making the required disclosures.
The federal law was not the first on the books that addressed the issue of registering convicted sex offenders. As early as 1947, California had laws that required sex offenders to be registered. Since the passage of the federal law in May of 1996, all states have passed some form of Megan's Law.