Biloxi (; French: [bilusi]) is a city in and one of two county seats of Harrison County, Mississippi, United States (the other seat being the adjoining city of Gulfport). The 2010 United States Census recorded the population as 44,054, and in 2019 the estimated population was 46,212. The area's first European settlers were French colonists. The city is part of the Gulfport–Biloxi metropolitan area and the Gulfport–Biloxi–Pascagoula, MS Combined Statistical Area. Prior to Hurricane Katrina, Biloxi was the third-largest city in Mississippi, behind Jackson and Gulfport. Due to the widespread destruction and flooding, many refugees left the city. Post-Katrina, the population of Biloxi decreased, and it became the fifth-largest city in the state, being surpassed by Hattiesburg and Southaven.The beachfront of Biloxi lies directly on the Mississippi Sound, with barrier islands scattered off the coast and into the Gulf of Mexico. Keesler Air Force Base lies within the city and is home to the 81st Training Wing and the 403d Wing of the U.S. Air Force Reserve.

Bay St. Louis is a city in and the county seat of Hancock County, Mississippi, in the United States. Located on the Gulf Coast on the west side of the Bay of St. Louis, it is part of the Gulfport–Biloxi Metropolitan Statistical Area. As of 2010, Bay St. Louis’ population was 9,260.

St. Bernard Parish (French: Paroisse de Saint-Bernard; Spanish: Parroquia de San Bernardo) is a parish located in the U.S. state of Louisiana. The parish seat and largest community is Chalmette. The parish was formed in 1807. St. Bernard Parish is part of the New Orleans–Metairie metropolitan statistical area. The parish is located southeast of New Orleans and comprises the Chandeleur Islands and Chandeleur Sound in the east. St. Bernard was the fastest growing parish in Louisiana from 2010 to 2020, increasing from a population of 35,897 in the 2010 census to 43,764 in 2020. It remains at less than two-thirds of its 2000 population of 67,229, prior to Hurricane Katrina.

St. John the Baptist Parish (SJBP, French: Paroisse de Saint-Jean-Baptiste) is a parish located in the U.S. state of Louisiana. At the 2020 census, the population was 42,447. The parish seat is Edgard, an unincorporated area, and the largest city is LaPlace, which is also unincorporated. St. John the Baptist Parish was established in 1807 as one of the original 19 parishes of the Territory of Orleans, which became the state of Louisiana.St. John the Baptist Parish is part of the New Orleans–Metairie metropolitan statistical area. This was considered part of the German Coast in the 18th and 19th centuries, named for numerous German immigrants who settled along the Mississippi River here in the 1720s. On January 8, 1811, the largest slave insurrection in US history, known as the German Coast Uprising, started here. It was short-lived, but more than 200 slaves gathered from plantations along the river and marched through St. Charles Parish toward New Orleans. This is part of the Sugarland or sugar parishes, which were devoted to sugar cane cultivation. Planters used large numbers of enslaved African-American workers before the war, and numerous freedmen stayed in the area to work on these plantations afterward. The parish includes three nationally significant examples of 19th-century plantation architecture: Evergreen Plantation, Whitney Plantation Historic District, and San Francisco Plantation House.