Postal Matter

Postal Matter in the United States

US Postal Service Classifications of Postal Matter

Introduction to Postal Matter

Mailable matter in the domestic service is divided into four classes, for which different rates are charged. First-class mail includes letters, postcards, matter wholly or partly in writing, and matter sealed or closed against inspection; second-class mail comprises newspapers and periodical publications; third-class mail (less than 16 oz/170 g) includes books, circulars, matter wholly in print, and proof sheets; and fourth-class mail (domestic parcel post, 16 oz or over) covers merchandise and all matter not covered in the other three classes. Express mail, the newest service, provides overnight delivery for packages of up to 70 lb. Letters and postcards sent by airmail to foreign countries are considered first-class mail, as are parcels sent by air or as registered mail. Additional fees are charged for special delivery or special handling. No airmail category exists for first-class letters within the United States.” (1)

Postal Abbreviations

The full list of U.S. postal abbreviations are posted on the Internet by the U.S. Postal Service at (

In addition, the two-letter postal abbreviations for the 50 states are listed in the World Almanac, the front of the National Zip Code Directory, The New York Public Library Reference Guide and probably many other places. You can also get the abbreviation for any particular state by looking at the addresses in most geographically organized directories (e.g., the AALL Directory & Handbook or the State Yellow Book).

Postal Rates

Current U.S. postal rates are posted in the Prices section of the U.S. Postal Service Web site. The USPS also posts historical postage rates and a Postage Price Calculatorfor domestic and international retail prices.

Postal or Zip Codes

United States: You can look up a U.S. Zip Code using the Postal Service’s ZIP Code Lookup. You could also use the National 5-Digit ZIP Code and Post Office Directory, which you’ll find in large libraries and post offices.

You can also look up the zip codes found in each county or city.

Canada: For Canadian postal codes, use the Postal Code Look-Up from Canada Post.


See Also

  • United States Postal Service
  • Demographics

Notes and References

  1. Information about Postal Matter in the Encarta Online Encyclopedia

Guide to Postal Matter

Postal Matter: Open and Free Legal Research of US Law

Federal Primary Materials

The U.S. federal government system consists of executive, legislative, and judicial branches, each of which creates information that can be the subject of legal research about Postal Matter. This part provides references, in relation to Postal Matter, to the legislative process, the federal judiciary, and the primary sources of federal law (cases, statutes, and regulations).

Federal primary materials about Postal Matter by content types:

Laws and Regulations

US Constitution
Federal Statutory Codes and Legislation

Federal Case Law and Court Materials

U.S. Courts of Appeals
United States courts of appeals, inclouding bankruptcy courts and bankcruptcy appellate panels:

Federal Administrative Materials and Resources

Presidential Materials

Materials that emanate from the President’s lawmaking function include executive orders for officers in departments and agencies and proclamations for announcing ceremonial or commemorative policies. Presidential materials available include:

Executive Materials

Federal Legislative History Materials

Legislative history traces the legislative process of a particular bill (about Postal Matter and other subjects) for the main purpose of determining the legislators’ intent behind the enactment of a law to explain or clarify ambiguities in the language or the perceived meaning of that law (about Postal Matter or other topics), or locating the current status of a bill and monitoring its progress.

State Administrative Materials and Resources

State regulations are rules and procedures promulgated by state agencies (which may apply to Postal Matter and other topics); they are a binding source of law. In addition to promulgating regulations, state administrative boards and agencies often have judicial or quasi-judicial authority and may issue administrative decisions affecting Postal Matter. Finding these decisions can be challenging. In many cases, researchers about Postal Matter should check state agency web sites for their regulations, decisions, forms, and other information of interest.

State rules and regulations are found in codes of regulations and administrative codes (official compilation of all rules and regulations, organized by subject matter). Search here:

State opinions of the Attorney General (official written advisory opinions on issues of state law related to Postal Matter when formerly requested by a designated government officer):

Tools and Forms

Law in Other Regions

*This resource guide is updated frequently. However, if you notice something is wrong or not working, or any resources that should be added, please notify us in any of the "Leave a Comment" area.

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