Oklahoma Abbreviation: OK and Okla.

Oklahoma abbreviation choices at a glance

A handy rule: machines get OK, and people usually get the full name. Okla. sits in the middle, for print and reference work where space is short but a two letter code would look too bare.

Using OK on mail and online forms

Two letter state codes arrived in the 1960s, alongside ZIP codes, so that sorting machines could read addresses fast. The Postal Service asks for OK in capitals, with no period and no space between the letters, placed right before the ZIP code.

Driver's license records, tax forms and checkout pages all use the same code. If a box allows only two characters, OK is the one and only answer for this state. Lowercase ok or a period, as in O.K., can confuse a scanner.

What is the abbreviation for Oklahoma in AP style?

News writers who follow AP style spell out Oklahoma inside a story. For a shortened name in an opening dateline, a photo caption or a sports list, the AP form is Okla.

Many legal citations, older textbooks and library catalogs use Okla. too. It is a true abbreviation of the word rather than a code made for sorting machines, which is why it keeps a capital O, lowercase letters after it and a closing period. Our guide to how to abbreviate explains why shortened words often end with a period.

OK, OH, OR: codes that trip people up

Ohio, Oklahoma and Oregon all begin with O, so a hurried typist can grab the wrong pair.

• OK is Oklahoma. Traditional form: Okla.
• OH is Ohio. The name is short, so it is usually spelled out in text. See the Ohio abbreviation page.
• OR is Oregon. Traditional form: Ore. More on the Oregon abbreviation page.
• OA and OL are not state codes, though people sometimes guess them.

Mail with the wrong pair may wander for days, so a quick glance at the ZIP code helps. Oklahoma ZIP codes start with 73 or 74.

Is OK for Oklahoma the same as okay?

No. The postal code was chosen because O and K are the first two letters of the state's name. The word OK, meaning all right, has its own separate history in American slang. The match is a happy accident.

Fans and businesses in the state enjoy the pun, and you will see it on shirts, signs and sports banners. In formal writing, though, do not use OK as shorthand for the state inside a sentence. Write "She moved to Oklahoma," not "She moved to OK," so readers do not stumble.

Facts behind the Sooner State

Oklahoma became the 46th state in 1907. Its capital and largest city is Oklahoma City, and Tulsa is the second largest. The name is usually traced to two Choctaw words, okla and humma, often translated as "red people." The nickname, the Sooner State, refers to settlers who slipped into the land before the official start of the land runs.

Many Native nations have their headquarters in Oklahoma, so you may see tribal names and abbreviations alongside the state code on local documents. For every state code in one place, open the state abbreviations list.

Quick rules for the abbreviation for Oklahoma

1. Use OK on anything addressed, scanned or typed into a two letter box.
2. Use Okla. in datelines, citations and crowded charts.
3. Spell out Oklahoma in regular sentences, even in a casual email to a coworker.
4. Never write O.K. or Ok. for the state, since those look like the word okay.
5. Pick one style per document and hold to it throughout.