| Parish | 1990 | 2000 | 2010 | 2020 | % Change (1990-2000) % | % Change (2000-2010) % | % Change (2010-2020) % |
| Washington | 43,185 | 49,566 | 51,133 | 46,582 | 14.77 | 3.16 | 8.9 |
| Tangipahoa | 85,709 | 83,302 | 98,890 | 133,777 | −2.80 | 18.71 | 35.28 |
| St. Tammany | 144,508 | 191,268 | 237,867 | 258,111 | 32.35 | 24.36 | 8.51 |
| St. John the Baptist | 39,996 | 30,841 | 34,402 | 43,184 | −22.88 | 11.54 | 25.53 |
| Orleans | 496,938 | 484,674 | 351,222 | 391,006 | −2.46 | −27.53 | 11.33 |
| St. Charles | 42,437 | 29,418 | 32,064 | 52,879 | −30.67 | 8.99 | 64.92 |
| St. Bernard | 66,631 | 67,229 | 37,764 | 46,721 | 0.89 | −43.82 | 23.72 |
| LaFourche | 85,860 | 60,255 | 62,054 | 98,115 | −29.82 | 29.85 | 58.11 |
| Plaquemines | 25,575 | 26,757 | 25,106 | 23,410 | 4.62 | −6.17 | −6.76 |
| Terrebonne | 96,982 | 72,392 | 77,923 | 111,021 | 25.35 | 7.64 | 42.48 |
| Jefferson | 448,306 | 438,731 | 417,828 | 434,051 | −2.13 | −4.76 | 3.9 |
| Total | 1,576,127 | 1,534,433 | 1,426,253 | 1,638,857 | −2.65 | −7.05 | 14.91 |