Ten years ago (2007), the city of Metropolis (DE) came under attack from the first wave of an invasion attack of parademons from the ruler of Apokolips; Darkseid. The protector of Metropolis known as Superman, soon found that the forces were too much for him. However, others soon arrived at the scene: Batman; the Flash; Green Lantern; Wonder Woman; Aquaman and Martian Manhunter. After defeating the onslaught of parademons and Darkseid himself, the seven heroes banded together and formed the Justice League.
Using a satellite, dubbed the Watchtower, as their base of operations and an old S.T.A.R Labs hanger outside of Central City (MO), dubbed the Hall of Justice, as their public front, with Zeta-Beam technology developed by scientist Adam Strange of S.T.A.R Labs, used to transport the League between the two locations. As the team grew over the years, more Zeta-Beam tubes were built in places such as Star City, Metropolis, and Gotham City.
Zeta-Beam Designations of the Justice League