GO trainers were able to unlock two legendary Pokémon, namely, Lugia and Articuno, as well as other in-game bonuses, after the recent Pokémon GO fest that was held in Grant Park, Chicago.
There are a couple of in-game rewards that were unlocked during the said event which are now available for the entire Pokémon GO community until Monday, July 24, at 5:00 P.M. PDT (Pacific Time), such as: double Stardust, double Candy, double XP, Increased Pokémon encounters, reduced hatching distance, and reduced buddy distance.
To celebrate Team Mystic’s victory on bagging the highest number of Pokémon caught, Articuno will join Lugia in Raid Battles everywhere starting immediately. Another two legendary Pokémon Zapdos and Moltres will be added to the game soon.
Source: Niantic