The Raft is a super-security prison located on a separate island at Ryker's Island Prison, with the objective to hold a vast amount of super-powered criminals, for example: Scarecrow, Controller, the U-Foes, Karl Lykos (Sauron), Crusader, Hydro-Man, Carnage (Cletus Kasady) and also contained the weak-minded Sentry. The facility has multiple underwater cell blocks, hi-tech steel windowless cells, two way relay video surveillance and super-powered S.H..I.E.L.D agents accompanying any no super visitors.
Electro was once hired to launch a break-out to free Karl Lykos, the break out triggered a battle involving Spider-Woman, Captain America, Spider-Man, The Sentry, Daredevil, Luke Cage, and Iron Man looking to regain control of the facility and return forty two escaped inmates, this event unintentionally created the New Avengers.
The Raft is perhaps the top super-powered criminals prison establishment of the U.S. Most escaped during the breakout but were recaptured. It was also a target for the Skrulls during Secret Invasion.
Following Siege, the Avengers U.S.Agent replaced Montgomery Battle as the facility's Warden and the Raft became home to the Thunderbolts Program with select inmates being able to work towards parole by participating in the program.
During Fear Itself, it was destroyed by The Juggernaut after he became the seemingly mindless Kuurth, Breaker of Stone, releasing almost all of the inmates in process.
The Raft was shown rebuilt following Juggernaut's rampage and since the disappearance of John Walker, it is unknown who is the current Warden of the prison.
Recently mayor J. Jonah Jameson had decided that the Raft was to dangerous to keep open and had planned to shut it down after the execution of the spider slayer, Alistair Smythe. However the Superior Spiderman (Doctor Octopus) had other plans, using a video recording of Jameson telling him to kill Smythe he blackmailed him into giving him the Raft as his own personal superhero HQ, which he has renamed Spider-Island II.
In Other Media
The Raft appears in the opening episodes of the series, where it is being used to house high profile supervillains like Graviton, Baron Zemo, the Purple Man and Arnim Zola. The prison is destroyed during Graviton's escape.
The Raft appears in the movie as a massive underwater prison designed for dangerous criminals. Falcon, Hawkeye, Scarlet Witch and Ant-Man are imprisoned in the facility after being defeated by Team Iron Man, a fact which greatly disturbs Tony Stark. At the close of film, Captain America attacks the prison and liberates his allies.