Optically stimulated luminescence (OSL) dating beach ridge sediments is one method for resolving barrier island growth at intermediate scales (decades-centuries), information that is lacking for Louisiana. This research combines OSL, GPR, aerial imagery, and cores to document temporal and spatial evolution of a Louisiana barrier island. Grand Isle is composed of beach ridges organized in distinct, unconformable sets that began forming 0.75 ka until 0.575 ka when deposition ceased, the ridges were partially eroded, and deposition resumed in a more eastward direction. The central ridges formed between 370±30 and 170±10 years ago at a rate of one ridge every 11.6 years with sand from the eroding Caminada headland that, with flanking barriers, forms the Bayou Lafourche transgressive depositional system. Grand Isle’s lithosome (92,600,000 cubic meters) requires an annual longshore transport of 128,625 cubic meters. The lithosome thickness (10 meters) and steady sediment supply stabilize the island relative to other Louisiana barriers.