The boundaries of the Republic of West Florida included all territory south of parallel 31°N, east of the Mississippi River, and north of the waterway formed by the Iberville River, Amite River, Lake Maurepas, Pass Manchac, Lake Pontchartrain, and the Rigolets. The Pearl River, with its branch that flowed into the Rigolets, formed the eastern boundary of the republic. A military expedition from the republic attempted but failed to capture the Spanish outpost at Mobile, which was situated between the Pearl and the Perdido River, farther to the east. Despite its name, none of the Republic of West Florida was within the borders of the present-day state of Florida, but rather entirely within the present borders of Louisiana.