Rockfort Island is believed to have been owned by Umbrella Corporation. Rockfort Island is an illegal prison camp with private-military training facilities.
Besides the prison and training facility, the island also features a large subterranean airport holding several C-130 sea-capable cargo planes, at least two harrier jets owned personally by Alfred. Several laboratories and B.O.W. stores are located within the island, including a supply of T-Viruses, and at least one T-078 Tyrant variant.
The island population consisted mostly of a mixture of assorted workers, trainees, guards, attendant staff and prisoners. During the outbreak, nearly every single one of them became zombies.
 Extra Info
Rockfort island training facility is still standing, but still is in bad shape. The facilities are only half destroyed, and under the total control of Albert Wesker. Chris Redfield manages to find Raval, alive but wounded, in an underground cavern below the training facility (Raval dies after saving him from the Grup worm).
Chris encounters Wesker and finds out that Claire flew to the Antarctic, Chris accesses the second Harrier and follows Claire to the Antarctic in order to save her.
Rockfort Island is abandoned, no one yet knows about it’s existence or if it was destroyed or not.