Significant events for area code 504
| Date |
Details |
| 1947 | The original area code for Louisiana |
| 1957 | Area code 504 split with 318 covering all of the western area, extending to both the northern and southern borders of the state |
| August, 1998 | Area code 504 split with 225 covering all of the western area of the then 504 area |
| 2001 | Area code 504 split with 985 covering all of the northeastern area of the lower area of the state |