NPA Codes in USA starting with 3
| NPA | Country | Time Difference (From GMT) | State | State Abbrv. | Service Date | Comments |
| 301 | USA | -5 | Maryland | MD | | |
| 302 | USA | -5 | Delaware | DE | | |
| 303 | USA | -7 | Colorado | CO | | |
| 304 | USA | -5 | West Virginia | WV | | |
| 305 | USA | -5 to -6 | Florida | FL | | |
| 307 | USA | -7 | Wyoming | WY | | |
| 308 | USA | -6 | Nebraska | NE | | |
| 309 | USA | -6 | Illinois | IL | | |
| 310 | USA | -8 | California | CA | 02 Nov 1991 | |
| 312 | USA | -6 | Illinois | IL | | |
| 313 | USA | -5 | Michigan | MI | | |
| 314 | USA | -5 | Missouri | MO | | |
| 315 | USA | -5 | New York | NY | | |
| 316 | USA | -6 | Kansas | KS | | |
| 317 | USA | -5 | Indiana | IN | | |
| 318 | USA | -6 | Louisiana | LA | | |
| 319 | USA | -6 | Iowa | IA | | |
| 320 | USA | -6 | Minnesota | MN | 17 Mar 1996 | |
| 321 | USA | -5 to -6 | Florida | FL | 01 Nov 1999 | |
| 323 | USA | -8 | California | CA | 13 Jun 1998 | |
| 325 | USA | -6 to -7 | Texas | TX | 05 Apr 2003 | |
| 327 | USA | -6 | Arkansas | AR | 20 Oct 2012 | |
| 330 | USA | -5 | Ohio | OH | 09 Mar 1996 | |
| 331 | USA | -6 | Illinois | IL | 07 Oct 2007 | |
| 332 | USA | -5 | New York | NY | 10 Jun 2017 | |
| 334 | USA | -6 | Alabama | AL | 15 Jan 1995 | |
| 336 | USA | -5 | North Carolina | NC | 15 Dec 1997 | |
| 337 | USA | -6 | Louisiana | LA | 11 Oct 1999 | |
| 339 | USA | -5 | Massachusetts | MA | 02 May 2001 | |
| 346 | USA | -6 | Texas | TX | 01 Jul 2014 | |
| 347 | USA | -5 | New York | NY | 01 Oct 1999 | |
| 351 | USA | -5 | Massachusetts | MA | 02 May 2001 | |
| 352 | USA | -5 to -6 | Florida | FL | 03 Dec 1995 | |
| 360 | USA | -8 | Washington | WA | 15 Jan 1995 | |
| 361 | USA | -6 to -7 | Texas | TX | 13 Feb 1999 | |
| 364 | USA | -5 | Kentucky | KY | 03 Aug 2013 | |
| 380 | USA | -5 | Ohio | OH | 27 Feb 2016 | |
| 385 | USA | -7 | Utah | UT | 01 Jun 2008 | |
| 386 | USA | -5 to -6 | Florida | FL | 15 Feb 2001 | |
See World Zone 1 for explanation of "NPA"
Where shown:
| Time Diff. |
is with respect to GMT (UCT) |
Suspended
Pending
Proposed |
indicate the code is not in use: the "Service Date" has been delayed or not set |
| Service Date |
is the date code becomes (or became) effective. If no date is shown, the code was introduced before 1995 |