St. Mary County Demographics

A map of St. Mary County's Population by Race

Race	2024 Pop	2020 Pop	2024 %	2020 %
White	25,540	26,334	53.4%	53.3%
Black	13,765	14,950	28.8%	30.3%
Hispanic	4,705	4,524	9.8%	9.2%
Multiracial	2,510	1,848	5.2%	3.7%
Native American/Other	842	1,103	1.8%	2.2%
Asian	466	647	1.0%	1.3%

St. Mary County, Louisiana has an estimated population of 47,828, a decrease from the 49,406 recorded in the 2020 Census. The population is 53.4% White, 28.8% Black, 9.8% Hispanic, 5.2% Multiracial, 1.8% Native American/Other, and 1.0% Asian. This demographic dot map shows the population of St. Mary County, with one dot drawn for each person counted by the Census, color-coded by race.

St. Mary has become slightly more racially diverse since the 2020 Census. It is more diverse than Louisiana overall. Demographers use a diversity index to measure the probability that two randomly selected individuals belong to different racial or ethnic groups. In St. Mary County, that probability was 61.4% in 2020 and 61.9% in the most recent ACS estimates.

St. Mary County is ranked the 23rd most populous county in Louisiana, out of 64 counties. St. Mary County was ranked the 22nd most populous county in the 2020 Census.

St. Mary County's White Population

25,540 residents of St. Mary County, or 53.4% of the population, identify as White. The share of White residents in St. Mary County is slightly lower than in Louisiana overall, where 55.7% of the population is White. St. Mary County ranks 45th statewide in terms of White residents as a share of the population, out of 64 counties.

Since the 2020 Census, St. Mary County's White population has declined by an estimated 3.0%. White residents' share of St. Mary County's population has remained roughly unchanged at 53.4%.

St. Mary County is more White than neighboring Iberville County (46% White). St. Mary County is less White than neighboring Iberia County (56% White), Assumption County (63.9% White), St. Martin County (63.1% White), and Terrebonne County (63.8% White).

St. Mary County's Black Population

13,765 residents of St. Mary County, or 28.8% of the population, identify as Black. The share of Black residents in St. Mary County is comparable to the share in Louisiana overall, where 30.5% of the population is Black. St. Mary County ranks 29th statewide in terms of Black residents as a share of the population, out of 64 counties.

Since the 2020 Census, St. Mary County's Black population has declined by an estimated 7.9%. Black residents' share of St. Mary County's population has decreased from 30.3% to 28.8%.

St. Mary County is more Black than neighboring Assumption County (27.7% Black), St. Martin County (28.6% Black), and Terrebonne County (18.3% Black). St. Mary County is less Black than neighboring Iberia County (31% Black), and Iberville County (43.2% Black).

St. Mary County's Asian Population

466 residents of St. Mary County, or 1.0% of the population, identify as Asian. The share of Asian residents in St. Mary County is comparable to the share in Louisiana overall, where 1.7% of the population is Asian. St. Mary County ranks 19th statewide in terms of Asian residents as a share of the population, out of 64 counties.

Since the 2020 Census, St. Mary County's Asian population has declined by an estimated 28.0%. Asian residents' share of St. Mary County's population has remained roughly unchanged at 1.0%.

St. Mary County is more Asian than neighboring Assumption County (0.9% Asian), St. Martin County (0.8% Asian), and Iberville County (0% Asian). St. Mary County is less Asian than neighboring Iberia County (2.5% Asian), and Terrebonne County (1.1% Asian).

St. Mary County's Hispanic Population

4,705 residents of St. Mary County, or 9.8% of the population, identify as Hispanic. The share of Hispanic residents in St. Mary County is slightly higher than in Louisiana overall, where 7.2% of the population is Hispanic. St. Mary County ranks 5th statewide in terms of Hispanic residents as a share of the population, out of 64 counties.

Since the 2020 Census, St. Mary County's Hispanic population has grown by an estimated 4.0%. Hispanic residents' share of St. Mary County's population has increased from 9.2% to 9.8%.

St. Mary County is more Hispanic than neighboring Iberia County (5.6% Hispanic), Assumption County (4.3% Hispanic), St. Martin County (3.6% Hispanic), Iberville County (5.2% Hispanic), and Terrebonne County (7.2% Hispanic).

St. Mary County's Native American/Other Population

842 residents of St. Mary County, or 1.8% of the population, identify as American Indian/Alaska Native/Native Hawaiian/Pacific Islander/Other. The share of Native American/Other residents in St. Mary County is comparable to the share in Louisiana overall, where 1% of the population is Native American/Other. St. Mary County ranks 5th statewide in terms of Native American/Other residents as a share of the population, out of 64 counties.

Since the 2020 Census, St. Mary County's Native American/Other population has declined by an estimated 23.7%. Native American/Other residents' share of St. Mary County's population has remained roughly unchanged at 1.8%.

St. Mary County is more Native American/Other than neighboring Iberia County (0.8% Native American/Other), Assumption County (0.8% Native American/Other), St. Martin County (0.6% Native American/Other), and Iberville County (0.9% Native American/Other). St. Mary County is less Native American/Other than neighboring Terrebonne County (4.8% Native American/Other).

St. Mary County's Multiracial Population

2,510 residents of St. Mary County, or 5.2% of the population, identify as Multiracial. The share of Multiracial residents in St. Mary County is comparable to the share in Louisiana overall, where 3.8% of the population is Multiracial. St. Mary County ranks 15th statewide in terms of Multiracial residents as a share of the population, out of 64 counties.

Since the 2020 Census, St. Mary County's Multiracial population has grown by an estimated 35.8%. Multiracial residents' share of St. Mary County's population has increased from 3.7% to 5.2%.

St. Mary County is more Multiracial than neighboring Iberia County (4.1% Multiracial), Assumption County (2.4% Multiracial), St. Martin County (3.3% Multiracial), Iberville County (4.6% Multiracial), and Terrebonne County (4.8% Multiracial).

Sources: Most recent population estimates are from the 2020-2024 American Community Survey 5-Year Estimates. 2020 population counts and map data are from 2020 Census State Redistricting Data. Geographic data are from Census TIGER/Line Shapefiles.