Yahoo Chief Financial Officer Ken Goldman was in New York to do the honors.
The Yahoo.com domain debuted in January of 1995.
ABC7 News Reporter David Louie profiled founders Jerry Yang and David Filo when they were grad students at Stanford when they launched the search engine from their college dorm room.
VIDEO: David Louie gets inside scoop on Yahoo in 1995
The company claims 700 million people visit its website every month.
Meantime, Yahoo's involvement was good luck for the Nasdaq, which hit the 5,000 mark for this first time since the Spring of 2000, the height of the dot-com bubble.