Are you referring to the Tier system of offences or something different?

According to federal law, the Adam Walsh Act was signed into law in 2006, and outlines three "Tiers" based on the severity of the offender's underlying sex offense. The more serious the offense, the more often they are required to appear to register, and the longer time period they are required to register. Previous federal laws include:

Jacob Wetterling Act of 1994: Required all 50 states to implement sex offender and crimes against children registries. (No tier system)

Megans Law of 1996: Allowed states to make information on registries open records available to the public. (No tier system)

Several other federal laws were passed since, but the most significant was Adam Walsh. That being said, there are 50 different states, many of which have not substantially implemented the elements of Adam Walsh. Each state's sex offender registries are governed by their own state statutes. Federal funding is withheld from states that have not substantially implemented the elements of Adam Walsh.

So to answer your question: At the federal level, the Tier system was established in 2006. However, 50 different states have 50 different rules and regulations for their offender registries. Some states have not implemented a tier system. Some states have implemented different tier systems than the federal law. For example, some states require offenders to get a psychiatric evaluation to gauge their risk of re-offending. Based on that result, they are placed at a certain "Level" or "Tier". So it is really difficult to fully answer your question without doing legal research for all 50 states. It gets even more complicated when you add in tribal territories and other territories (like Puerto Rico).

Edit: I'm not a historian, but I am a police officer that maintains a large sex offender registry in the Midwest.