First Handheld Video Game System
The first handheld system was not the Game Boy -- and not by a long shot. However, Nintendo most certainly innovated the handheld market more than any other company, remaining the leading handheld producer to this day with the Nintendo 3DS.
Mattel's Handhelds
More Information:
- "Mattel Auto Race" - Wikipedia
- "Microvision" - Wikipedia
References:
1. Melanson, Donald. "A Brief History of Handheld Video Games." Engadget (2006)