Fortaleza Dearborn was a fortaleza established by the city-state of Gerrares during a wave of colonialism initiated by Tugal during the Median Era. Located on the Amarillo River on continent Moyen-Sud, a merchant named João Aurolliet founded the fortaleza to bypass the coastal Moyenese-Sud traders that marked up prices of goods coming from inland. Aurolliet's actions angered the traders, who captured the fort in the Fortaleza Dearborn massacre. Tugali traders in Gerrares did not notice that Aurolliet and his allies were dead, mistaking the Moyenese-Sud traders for Aurolliet's group; the traders took advantage of Aurolliet's trade connections to amass massive profits. However, as the fortaleza still technically pledged allegiance to Gerrares, growing suspicions between Gerrares and Simbopolis led Gerrares to tax their fortalezas heavily to fund a large standing army. This displeased the Moyenese-Sud traders greatly.

When the Tugali War of Unification broke out, the rulers of Fortaleza Dearborn declared independence from Gerrares as the city-state was destroyed. Contact with traders from the newly industrialized Despotate of Silvermoon gave rise to a massive population boom and rapid industrialization within the Dearbornian state itself. The city of Dearborn grew around the Fortaleza, which had become a massive citadel and the seat of government of the nation.

Dearborn's unchecked industrial policies polluted the Amarillo River to a terrible extent, poisoning much of the fertile land downstream. As famine came about, the Shecaguan War of Unification broke out as starved outer colonies formerly reliant on Dearborn's trade declared independence so that they might keep enough food (food normally exported to Dearborn as a tax) to feed their own inhabitants. Dearborn was deprived of food because of these events. Riots erupted in the city as Dearbornian inhabitants killed each other for mouthfuls of food or potable water. In the resulting civil conflict, Dearborn (including the Fortaleza) was razed by invaders from a coalition of outer colonies that later destroyed each other in war.

Michael Turner Bluff later returned to the site of Fortaleza Dearborn and re-established the city of Dearborn as the capital of the Centralized Republic of Shecagua.