History of video games/Game conventions

Foundational developments
A Cincinnati, Ohio duo debuts the first known modern cosplay in 1908. Near the end of the century, cosplay would become a staple at a number of events, including gaming conventions.

The first Consumer Electronics Show (CES) in 1967 employs women as "CES Guides", with this position later being recognized as the origin of the controversial "Booth Babe" of later conventions.

The first ACM SIGGRAPH (Association for Computing Machinery Special Interest Group on Computer Graphics) convention is held in Boulder, Colorado in 1974 to focus on computer graphics technology. Though computer graphics work would have an indirect effect on the gaming market, SIGGRAPH would later take more direct involvement in the gaming industry with dedicated symposiums on video games.

On December 21st, 1975 the first Comic Market (Comiket) is held at the Fire Defense Building in Tokyo, Japan to celebrate manga and to a lesser extent anime / Japanimation. While not a gaming convention per say, a number of important series saw their first releases at future Comikets, such as Comiket 52 in 1997 which saw the first Touhou game releases sold at a booth manned by Zun.

CES 1979 showcased a number of Atari computers. The Emerson Arcadia 2001 is debuted at CES 1982, and the Nintendo Entertainment System sees its North American Debut at CES 1985.

First video game focused conventions
25 developers meet at a house in 1988 for the first Game Developer Conference (GDC).

The first Nintendo Spaceworld convention is held in 1989.

1990's
The first Assembly demoparty is held in 1992.

Supergames was a major industry event in Paris - 1993.

The first Electronics Entertainment Expo (E3) is held in 1995.

The first Tokyo Game Show is held at Big Sight in Tokyo Japan in August of 1996.

2000's
The first MAGFest (then known as the Mid-Atlantic Gaming Festival) is held in September 2002.

The first Penny Arcade Expo (PAX) is held in 2004.