The United States Postal Service (USPS), also known as the Post Office, U.S. Mail, or Postal Service, is an independent agency of the executive branch of the United States federal government responsible for providing postal service in the U.S., its insular areas, and its associated states. It is one of the few government agencies explicitly authorized by the Constitution of the United States. The USPS, as of 2021, has 516,636 career employees and 136,531 non-career employees.
A postal code is a series of letters or digits or both, sometimes including spaces or punctuation, included in a postal address for the purpose of sorting mail.
A ZIP Code is a system of postal codes used by the United States Postal Service (USPS). Introduced on July 1, 1963, the basic format consisted of five digits. In 1983, an extended ZIP+4 code was introduced; it included the five digits of the ZIP Code, followed by a hyphen and four digits that designated a more specific location.
POSTNET is a barcode symbology used by the United States Postal Service to assist in directing mail. The ZIP Code or ZIP+4 code is encoded in half- and full-height bars. Most often, the delivery point is added, usually being the last two digits of the address or PO box number.
In a postal system, a delivery point is a single mailbox or other place at which mail is delivered. It differs from a street address, in that each address may have several delivery points, such as an apartment, office department, or other room. Such buildings are often called multiple-dwelling units (MDUs) by the USPS.
A post office box is a uniquely addressable lockable box located on the premises of a post office.
Bulk mail broadly refers to mail that is mailed and processed in bulk at reduced rates. The term is sometimes used as a synonym for advertising mail.
An address is a collection of information, presented in a mostly fixed format, used to give the location of a building, apartment, or other structure or a plot of land, generally using political boundaries and street names as references, along with other identifiers such as house or apartment numbers and organization name. Some addresses also contain special codes, such as a postal code, to make identification easier and aid in the routing of mail.
The Coding Accuracy Support System (CASS) enables the United States Postal Service (USPS) to evaluate the accuracy of software that corrects and matches street addresses. CASS certification is offered to all mailers, service bureaus, and software vendors that would like the USPS to evaluate the quality of their address-matching software and improve the accuracy of their ZIP+4, carrier route, and five-digit coding.
Freepost is a postal service provided by various postal administrations, whereby a person sends mail without affixing postage, and the recipient pays the postage when collecting the mail. Freepost differs from self-addressed stamped envelopes, courtesy reply mail, and metered reply mail in that the recipient of the freepost pays only for those items that are actually received, rather than for all that are distributed. Freepost of preprinted cards issued by businesses is also different from postal stationery sold by postal administrations.
The Postal Transportation Service (PTS) was the renamed successor to the Railway Mail Service of the United States Post Office Department from October 1, 1949. Although this branch of the service had been in charge of all transit mail, some parts had little to do with railroads, even though they were still the most important part of the service. In 1950, of the 32,000 clerks assigned to the PTS, only about 16,000 actually worked on trains. The remainder were in terminals, transfer offices, Air Mail Facility, Highway Post Offices (HPO), administrative offices, etc. Boat Railway Post Office, Streetcar Railway Post Offices, and the Seapost Service had already been discontinued. The name of the Chief Clerk's office was changed to District Superintendent's office.
ZIP Code Tabulation Areas (ZCTAs) are statistical entities developed by the United States Census Bureau for tabulating summary statistics. These were introduced with the Census 2000 and continued with the 2010 Census and 5 year American Community Survey data sets. This new entity was developed to overcome the difficulties in precisely defining the land area covered by each ZIP code. Defining the extent of an area is necessary in order to tabulate census data for that area.
A destination sectional center facility (SCF) is a processing and distribution center (P&DC) of the United States Postal Service (USPS) that serves a designated geographical area defined by one or more three-digit ZIP Code prefixes. A sectional center facility routes mail between local post offices and to and from network distribution centers (NDCs) and Surface Transfer Centers (STCs), which form the backbone of the network.
Southeastern was a United States Postal Service regional Processing and Distribution Center (P&DC) in Tredyffrin Township, Chester County, Pennsylvania, United States, near Devon. It was primarily known for its post mark on mail originating in many ZIP codes in the region. The retail post office remains open at the location of the former P&DC.
The Intelligent Mail Barcode (IMb) is a 65-bar barcode for use on mail in the United States. The term "Intelligent Mail" refers to services offered by the United States Postal Service for domestic mail delivery. The IM barcode is intended to provide greater information and functionality than its predecessors POSTNET and PLANET. An Intelligent Mail barcode has also been referred to as a One Code Solution and a 4-State Customer Barcode, abbreviated 4CB, 4-CB or USPS4CB. The complete specification can be found in USPS Document USPS-B-3200. It effectively incorporates the routing ZIP Code and tracking information included in previously used postal barcode standards.
A sorting office or processing and distribution center is any location where postal operators bring mail after collection for sorting into batches for delivery to the addressee, which may be a direct delivery or sent onwards to another regional or local sorting office, or to another postal administration.
Postal address verification is the process used to check the validity and deliverability of a physical mailing address. According to the United States Postal Service, an address is valid if it is CASS-certified, meaning that it exists within the comprehensive list of mailable addresses in their Address Management System. This is different from the credit card Address Verification System (AVS), which is the method used by credit card processors to authenticate ownership of a credit card by verifying that the account on the credit card matches the billing address on file. Credit card AVS does not determine deliverability of an address.
Address Management System (AMS) is the United States Postal Service master database of deliverable addresses. Address-checking tools using AMS provide address standardization, as well as city/state and ZIP Code lookup features.
Jersey City, NJ 
Jacksonville, FL 
Springfield, MA 
Philadelphia, PA 
Capitol Heights, MD 
Greensboro, NC 
Atlanta, GA 
Cincinnati, OH 
Memphis, TN 
Hazelwood, MO 
Allen Park, MI 
Forest Park, IL 
Eagan, MN 
Des Moines, IA 
Denver, CO 
Kansas City, KS 
Dallas, TX 
Federal Way, WA 
Bell Gardens, CA 
