The parish is split into two non-contiguous parts, because of a surveying error dating to 1868, when Iberia Parish was created by the Louisiana Legislature. St. Martin has the highest percentage of French-speaking residents of any county or parish in the United States.

St. Martin Parish was established in 1807, five years before Louisiana was admitted into the Union. In the late 1700's, French immigrants from Canada and France moved into the area, laying the bases for two local myths—the Evangeline story and the migration of French aristocrats to the banks of Bayou Teche. British eviction of French settlers in Canada after the French and Indian War resulted in many Acadian farmers settling in Louisiana. Henry Wadsworth Longfellow's epic poem Evangeline immortalized the Acadian exile from Nova Scotia, and created two mythical lovers, Evangeline and Gabriel. According to local tradition, a few years later, French Royalists, in an effort to escape the horrors of the French Revolution, settled in the same region, supposedly re-creating a society of wealth and luxury that became known as "Le Petit Paris." Although the Evangeline and Petit Paris stories are legends, both play a major role in the continuing historic appeal of St. Martin Parish.