[3] St. Mary Parish comprises the Morgan City, LA Micropolitan Statistical Area, which is also included in the Lafayette-Opelousas-Morgan City, LA Combined Statistical Area.

[4] Cypremort Point State Park is located in the parish on Vermilion Bay.

[5] As of the 2020 United States census, there were 49,406 people, 19,856 households, and 11,354 families residing in the parish.

23.20% of all households were made up of individuals, and 8.70% had someone living alone who was 65 years of age or older.

The Chitimacha Day School, affiliated with the Bureau of Indian Education (BIE), is in the Charenton community of unincorporated St. Mary Parish.

B Company 2-156TH Infantry Battalion of the 256TH IBCT resides in Franklin, Louisiana.

Since 2008, the county has become more Republican leaning, with Donald Trump breaking 60% of the vote in both of his runs.