Mariana County is a fictional county set to appear in Grand Theft Auto VI (Rockstar Games, 2026), located in the southern region of the fictional State of Leonida, Rockstar's in-universe analogue of Florida. First revealed in passing on an Interstate 404 signpost in Port Gellhorn during the game's second official trailer (Rockstar Games, 2025), Mariana County has since been confirmed as the governmental jurisdiction encompassing two of the most marketed regions on the GTA VI promotional website: the Grassrivers wetlands and the Leonida Keys archipelago (GTA Wiki, 2026a). Its real-world counterpart is widely identified as Monroe County, Florida, the southernmost county in the United States and the administrative home of the Florida Keys and the bulk of Everglades National Park (Wikipedia, 2025). The implications of this analogy are substantial: Mariana County is positioned to deliver Rockstar's most ambitious treatment of mangrove swamp, coral-key, and open-water gameplay to date, surpassing the comparatively narrow keys content of GTA: Vice City Stories and the limited swampland of GTA V's Blaine County in both fidelity and scope.
Mariana County is one of several confirmed counties making up the State of Leonida, sitting alongside Vice-Dale County (which contains Vice City proper), Kelly County (containing Port Gellhorn), Ambrosia County, Leonard County, and at least one unnamed northern county (GTA Wiki, 2026a). It occupies the southern and southwestern reaches of Leonida, forming a transitional zone between the urban density of Vice-Dale and the open Gulf and Atlantic waters that bound the state's peninsular geography. Two macro-regions are confirmed within its borders: the Grassrivers, a vast flooded grasslands ecosystem that bleeds northward into Vice-Dale County, and the Leonida Keys, a tropical archipelago that constitutes the southernmost landmass of the in-universe continental United States (GTA Wiki, 2026b; GTA Wiki, 2026c). Two named towns are presently confirmed inside the county: Key Lento, located in the Keys, and Watson Bay, a Grassrivers settlement (GTA Wiki, 2026a). East Key is an additional confirmed key within the archipelago.
This footprint maps closely onto Monroe County, Florida, which covers approximately 3,738 square miles, of which over 73 percent is water (Wikipedia, 2025). In Monroe County, more than 99.9 percent of the population lives on the Florida Keys, while the mainland portion is dominated by Everglades National Park and Big Cypress National Preserve and is virtually uninhabited (Wikipedia, 2025). Mariana County's bifurcation between the sparsely settled Grassrivers swamp and the more densely tourist-oriented Keys faithfully reproduces this geographic schism, suggesting Rockstar has chosen administrative authenticity over the more compressed county boundaries seen in earlier titles.
The coastal connection in Mariana County is not incidental; it is the defining feature of the jurisdiction. The Leonida Keys are explicitly described on Rockstar's promotional website as the "Gateway to Paradise," an archipelago of tropical islands accessible via the Keys Causeway, which arcs south-southwest from Vice-Dale County before bending westward over the Gulf of Mexico and the in-universe Straits of Leonida (Rockstar Games, 2025, cited in GTA Wiki, 2026c). This causeway is the direct analogue of the Overseas Highway (U.S. Route 1) connecting mainland Florida to Key West, and confirmed bridge structures within the Keys include a Bahia Honda-inspired rail bridge and a New Bahia Honda-inspired road bridge, signalling Rockstar's intent to recreate iconic Florida Keys infrastructure with high environmental fidelity (GTA Wiki, 2026c).
The Grassrivers component extends the coastal identity inland through brackish marsh, mangrove channels, and tidal estuary systems that link the Keys to the southern boundary of Vice City. Promotional copy describes the wetlands as a "primordial expanse" inhabited by alligators and "deadlier predators" (Rockstar Games, 2025, cited in GTA Wiki, 2026b), and the region's name is widely interpreted as a homage to Marjory Stoneman Douglas's seminal 1947 book The Everglades: River of Grass (Douglas, 1947). The implied presence of Hurricane Roxy in the region prior to the events of the game (GTA Wiki, 2026c) further roots Mariana County in a recognizably Floridian climatic reality, where tropical cyclone exposure shapes infrastructure, insurance markets, and human settlement patterns.
Multiple protagonist-adjacent characters are tied to Mariana County. Jason Duval, Lucia Caminos, Cal Hampton, and Brian Heder are all listed among the Leonida Keys' notable residents (GTA Wiki, 2026c), meaning at least one of the dual protagonists is expected to base significant gameplay arcs in the county. Combined with Key West's real-world reputation as a haven for transients, smugglers, sport fishermen, and the literary set (e.g., the Hemingway House), the cultural template available to Rockstar is rich with the seedy, sun-bleached Americana the studio has historically excelled at lampooning (Wikipedia, 2025).
Douglas, M.S. (1947) The Everglades: River of Grass. New York: Rinehart & Company.
GTA Wiki (2026a) 'Mariana County', GTA Wiki. Available at: https://gta.fandom.com/wiki/Mariana_County (Accessed: 14 May 2026).
GTA Wiki (2026b) 'Grassrivers', GTA Wiki. Available at: https://gta.fandom.com/wiki/Grassrivers (Accessed: 14 May 2026).
GTA Wiki (2026c) 'Leonida Keys', GTA Wiki. Available at: https://gta.fandom.com/wiki/Leonida_Keys (Accessed: 14 May 2026).
Rockstar Games (2025) Grand Theft Auto VI – Official Promotional Website. Available at: https://www.rockstargames.com/VI (Accessed: 14 May 2026).
Wikipedia (2025) 'Monroe County, Florida', Wikipedia, the Free Encyclopedia. Available at: https://en.wikipedia.org/wiki/Monroe_County,_Florida (Accessed: 14 May 2026).