In which year was the first game of the Sonic Adventure video game series released?
Sonic Adventure: Sonic Adventure is a platform video game developed by Sonic Team and published by Sega. Sonic Adventure:  Originally released for the Dreamcast, it was the first game in the main "Sonic the Hedgehog" series since "Sonic & Knuckles" (1994), and follows the respective quests of Sonic, Tails, Knuckles, Amy, E-102 Gamma, and Big to stop Doctor Ivo "Eggman" Robotnik from obtaining the seven Chaos Emeralds and releasing an ancient evil. Sonic the Hedgehog:  The first game in the series, released in 1991, was conceived by Sega's Sonic Team division after Sega requested a mascot character.
1991