The first .org domain name, mitre.org, was registered on July 10, 1985 by the MITRE Corporation, a non-profit organization that provides systems engineering, research and development, and information technology support to the government.
.org was one of the original six generic TLDs (others include .com, .net, .edu, .mil, and .int) and was started as an extension non-profit organizations, however it has always been available to the general public.
25 years later, more than 8.5 million .org domain names have been registered world wide.
.org was originally manged by Verisign, along with .com and .net. However, in 2003, .the Public Interest Registry (PIR), along with their partner, Affilias, took over the management of the TLD. Since then, registrations have reportedly jumped by 300%.