Keep in mind that not everyone is aware of the state registries and not everyone chooses to use them; consequently, searchers shouldn't depend solely on the state registry but may also wish to register with private organizations, such as the International Soundex Reunion Registry (ISSR).
More than half the states in the United States have some sort of registry that adopters may be able to use to find information about their birthparents (and vice versa), even without information on their birthparents' names. These registries generally are managed by the state social services department (usually located in the state capital or in the state vital statistics branch). I'll explain the different kinds of registries. (States continue to change their laws on matters related to adoption, including search, so don't assume that this information is cast in granite for all time. It isn't.)
If both an adopted adult (over 18 or, in some states, over 21) and a birthparent register in a state with a mutual consent registry (also known as a voluntary consent registry), identifying information will be provided to both.
The following states offer mutual consent registries (some states with registries may be missing from this list):
Search and Consent/Confidential Intermediary
A search and consent or confidential intermediary system is a system whereby one person, usually the adoptee, requests that a search be made for the birthparent. The birthparent is identified, contacted, and asked whether she or he wants contact with the adoptee. If the birthparent agrees, then the identifying information is provided to the adopted adult.
Some states provide a search and consent system, otherwise known as a confidential intermediary system. In this system, the adopted adult can request identifying information on the birthparents. The confidential intermediary locates the birthparents and asks for their permission to release identifying information. If they consent, the adopted adult is given their names. Some detractors have called this system “search and confront” because sometimes birthparents may be pressured into a rushed meeting by harried or inexperienced workers.
States that offer confidential intermediary systems, include the following:
Note that some states offer both a mutual consent registry and a confidential intermediary system.