Three Mile Island is a Mutant prison ran by William Stryker inside the eponymous nuclear power plant. There he experimented on them, and combined their powers into the "Weapon XI". Logan got there through former prisoner Remy LeBeau's plane, and with the assistance of Kayla Silverfox, got the prisoners free before battling Weapon XI. Both escaled one of the power plant's cooling towers, where Victor Creed arrived to help Logan