Grand Banks Steel Inc Foundry (also known as the East Los Santos Foundry) is a business in Grand Theft Auto V located in Cypress Flats/Murrieta Heights, East Los Santos. The three protagonists will use this foundry as the location for their planned climactic shootout in one of the alternative endings for the main storyline.
A large industrial steel foundry complex located in a block bounded by Labor Place, Murrieta Heights to the north, Orchardville Avenue to the west, El Rancho Boulevard, Cypress Flats to the south and Tower Way and the Elysian Fields Freeway to the east, the buildings are normally locked and inaccessible to players, unless the player elects option C (Deathwish) in the final chapter of the GTA V storyline, in which case the interior of the main foundry building is open briefly.
For some odd reason, what appear to be British goods wagons from the early-mid 20th Century are located in the rail yard. It is unknown what these are doing on an American rail system, as their small size limits how much they can carry (and thus, makes them economically inefficient, the main reason small wagonload freight was eliminated from the British railway network in the 1970s), and their hook-and-chain couplers are incompatible with knuckle couplers.
This might be a humorous pun on the name, as the acronym for the company is GB Steel Inc., GB seemingly standing for Great Britain.