The purpose of ZIP codes is to ensure an efficient postal delivery. Some mails would cross states and in such a cases, the military facility dealing with the multiple states or other remote areas that service the bordering states. The first three digits always designate the mail to a sectional center facility. It is at this point that further mail sorting is done to then it is sent to the distribution center. When we look at the ZIP codes in terms of geographic location such that the ZIP codes that begin with the digit ‘0’ are for New England, New Jersey Region. The 00501 ZIP codes are exclusively of US Internal Revenue Service Center. The ZIP codes for the lowest digits include the areas of Holtsville, New York.
Here is a list of the way the first digit of the ZIP code lookup is allocated to the states.
0 – New York (NY Fishers Island), Maine (ME), Massachusetts (MA) Connecticut( CT), New Hampshire (NH), Puerto Rico (PR), Vermont (VT), Army Post Office Europe (AE) , Virgin Islands, (VI) and Fleet Post Office Europe (AE).
1= New York (NY), Delaware (DE), Pennsylvania (PA)
2= Maryland(MD), District of Colombia (DC), North Carolina (NC), Virginia(VA), South Carolina (SC) and West Virginia (WV)
3= Florida (FL), Alabama (AL), Georgia (GA), Tennessee (TN), Mississippi (MS), Fleet Post Office Americas (AA) and Army Post Office Americas (AA)
4= Kentucky (KY), Indiana (IN), Michigan (MI) and Ohio (OH)
5= Minnesota (MT), Iowa (IA), North Dakota (ND), Montana (MT), Wisconsin (WI) and South Dakota (SD)
6= Kansas (KS), Missouri (MO), Illinois (IL) and Nebraska (NE)
7=Louisiana (LA), Texas (TX), Arkansas (AR) and Oklahoma (OK)
8= Colorado (CO), Arizona (AZ), Idaho (ID), Nevada (NV), New Mexico (NM), Wyoming (WY) and Utah (UT)
9= Washington (WA), Army Post Office Pacific (AP), Palau (PW), Oregon (OR)< Federated States of Micronesia (FM), Alaska (AK), California (CA), American Samoa (AS) , Hawaii (HI) and Marshall Islands (MH)
Finally, the number of ZIP codes is up to 42000 in the United States. These ZIP codes are used to track mail and for gathering geographical data of states within the United States. The USPA is so efficient, and it delivers mails to largest geographical areas than any other postal service in the world.