First National Archives Catalog online.
"The catalogue itself began to move online in 1998, the first national archive in the world to do so."
The United States National Archives and Records Administration had begun to move its catalog online well before 1998. See this entry from the Internet Archive from June 1997:
https://web.archive.org/web/19970606073326/http://www.nara.gov/nara/nail.html