Original 24 top-level NAICS categories:
| Code | Title |
| 11 | Agriculture, Forestry, Fishing and Hunting |
| 21 | Mining |
| 22 | Utilities |
| 23 | Construction |
| 31 | Manufacturing |
| 32 | Manufacturing |
| 33 | Manufacturing |
| 42 | Wholesale Trade |
| 44 | Retail Trade |
| 45 | Retail Trade |
| 48 | Transportation and Warehousing |
| 49 | Transportation and Warehousing |
| 51 | Information |
| 52 | Finance and Insurance |
| 53 | Real Estate and Rental and Leasing |
| 54 | Professional, Scientific, and Technical Services |
| 55 | Management of Companies and Enterprises |
| 56 | Administrative and Support and Waste Management and Remediation Services |
| 61 | Educational Services |
| 62 | Health Care and Social Assistance |
| 71 | Arts, Entertainment, and Recreation |
| 72 | Accommodation and Food Services |
| 81 | Other Services (except Public Administration) |
| 92 | Public Administration |
Have been merged into 9 prime NAICS categories:
| Code | Title |
| 1 | Agriculture, Forestry, Fishing and Hunting |
| 2 | Mining, Utilities and Construction |
| 3 | Manufacturing |
| 4 | Wholesale Trade, Retail Trade, Transportation and Warehousing |
| 5 | Information, Finance and Insurance, Professional, etc. |
| 6 | Educational Services, Health Care and Social Assistance |
| 7 | Arts, Entertainment, and Recreation, Accommodation and Food Services |
| 8 | Other Services (except Public Administration) |
| 9 | Public Administration |