Mariana County

Mariana County is the weakest-evidenced of Leonida's five counties, leaning mostly on datamined road signage rather than a clean trailer sighting. It corresponds to Florida's Monroe County — real Monroe is the Keys and the Everglades, which fits Mariana well — and sits in Leonida's south-west.

Mariana is anchored by two very different places: the Leonida Keys, an easygoing tropical archipelago connected to Vice City by the Keys Causeway, and the Grassrivers, a primordial Everglades analogue of mangroves, flooded grassland and airboats. The Keys are home turf for Jason Duval — Key Lento is his home — and a base for veteran smuggler Brian Heder; the Grassrivers are patrolled by the POACH wildlife-enforcement body.

Boundaries — and the county's existence as drawn — are rumor tier, not confirmed on-screen.