Basement geometry of the Eastern Gulf of Mexico developed following the breakup of Pangea and the opening of the Gulf of Mexico in Late Triassic time. Nine 2-D pre-stack depth migrated seismic profiles and a structural restoration provide insight into the evolution and development of the southern West Florida Basin, located west of the Florida Escarpment in the Eastern Gulf of Mexico. Seismic reflection profiles reveal basement structures probably developed following a combination of Late Triassic extension and extension and subsequent oceanic crust emplacement in Middle Jurassic time. During Late Triassic rifting, the West Florida Basin developed as a rift graben; however, the graben was later dissected during the Middle Jurassic drift episode. Absence of faulting, syn-rift deposition and sagging in the Lower Cretaceous seismic section indicates that extension and rotation of the Yucatán block must have stopped prior to Cretaceous time. After extension terminated and the Gulf of Mexico reached its modern day configuration, subsidence from lithospheric cooling and sediment loading dominated throughout Cretaceous time. A structural restoration confirms that following Late Triassic rifting, basement topography remains relatively elevated to the south in the West Florida Basin. Subsequent extension and subsidence further dissected the basement allowing for the deposition of Middle and Late Jurassic syn-rift and Cretaceous post-rift sediments. Because of the lack of well control in the West Florida Basin, seismic packages are correlated northward to the northern margin of the West Florida Basin and slope, the Tampa Embayment, and the Apalachicola Basin and southward to the Straits of Florida and Yucatán. Seismic interpretations reveal two syn-rift packages, Triassic-Jurassic (TJ) and Jurassic-Cretaceous (JK), and one post rift package, Early Cretaceous (EK), were deposited prior to the Mid-Cretaceous Sequence Boundary, a basin-wide unconformity that marks the termination of subsidence related to lithospheric cooling. These seismic packages are the southern equivalents of stratigraphy in the northeastern Gulf of Mexico, and may include the petroliferous Norphlet and Smackover Formations. Oceanic or `proto-oceanic' crust in a transitional zone between oceanic and continental crust is interpreted in central West Florida Basin, where there is little brittle faulting and a change in seismic character of basement. This interpretation is further validated by bright basinward shallowing reflectors within the basement that may represent a Moho/detachment that facilitated extension and oceanic crust emplacement.