In the 1980s, the National Science Foundation's (NSF's) high-speed network, the NSFNET, was connected to the Advanced Research Projects Agency (ARPA, now DARPA) wide area network known as ARPANET. Originally a U.S. Department of Defense network, it essentially formed the infrastructure of what we now know as the Internet.
During these early days, the administrative task of assigning addresses was handled by one individual, Jon Postel, on a volunteer basis. When the task grew too large, the Internet Assigned Names and Numbers Authority (IANA) was established as the "custodian" of Internet addresses, along with an Internet Registry function to handle the registration tasks.
This IR function was contracted first to USC/ISI and then to SRI International before it was awarded in 1991 to Network Solutions, Inc. (NSI) in Herndon, Virginia. This contract included the services of IP address and domain name registration and support, Autonomous System (AS) number registration, user registration, online information services, help desk operations, RFC and Internet-Draft archives, and distribution services.
In 1993, following several years of explosive Internet growth, the U.S. government and the NSF decided that network support for the commercial Internet should be separated from the U.S. Department of Defense. The NSF originated a project named InterNIC under a cooperative agreement with NSI to provide registration and allocation of domain names and IP address numbers.
Over time, the general Internet community reached a consensus to separate the management of domain names from the management of IP numbers, in part to maintain stability of the IP numbering system. As a result, ARIN was established to provide IP registration services as an independent, nonprofit corporation, and opened its doors for business on 22 December 1997.
For more information about the history of Regional Internet Registries, please read the article "Development of the Regional Internet Registry System," as published in the Cisco Internet Protocol Journal, December 2001.