1 The rule in plain terms
The rule is simple to state and easy to apply once you know the shape. In running text, spell out the names of states and set them off with commas when they follow a city: She moved to Austin, Texas, last spring. Abbreviate a state only when it appears in a dateline, a table, a list, a mailing address, or a short-form identification such as Sacramento, Calif. Street addresses take figures for the building number and spelled-out or abbreviated street-type words according to the entry: 400 Broad St., 12 Oak Ave., 7 Maple Lane. Do not put a comma between the street number and the street name, and do not abbreviate Street, Avenue, or Boulevard when they stand alone without a number.
Phone numbers take hyphens, not periods, parentheses, or spaces: 206-555-0142. Use the area code whenever the number could be dialed from outside the immediate area, and drop it only when every reader in the audience shares that code. Extension numbers follow a comma and the abbreviation ext.: 206-555-0142, ext. 17. The same logic governs addresses: keep them tight, keep them consistent, and let the punctuation do the work of separating the parts.
2 Why editors enforce it
Readers do not admire consistency; they simply notice its absence. A story that spells out California in one paragraph and shortens it to Calif. in the next makes the reader pause, and a pause is a small tax on attention. Editors enforce these forms because they remove that tax. The address, phone number, and state are the places where a reader is most likely to act on the information, whether by mailing a letter, placing a call, or looking up a location, so the cost of an inconsistent form is higher here than almost anywhere else in a story.
There is also a practical reason. Copy moves through several hands before it reaches print or post, and each hand makes small decisions. A house rule about state abbreviations and phone punctuation means those decisions are already made, which speeds the desk and reduces the chance that two versions of the same fact appear in one piece. Consistency is not decoration; it is a form of accuracy. When the form is stable, the reader trusts the content, and the desk spends its time on substance rather than on re-punctuating a phone number for the third time.
3 Where writers usually slip
The most common slip is abbreviating a state name in running text. A writer types Los Angeles, Calif., because the abbreviation feels compact, but the house rule reserves that form for datelines, lists, tables, and short-form identifications. The fix is to spell it out: Los Angeles, California. The second slip is the missing comma pair. When a state follows a city, it is parenthetical, so it needs a comma on each side: She flew to Denver, Colorado, on Tuesday. Writers often supply the first comma and forget the second, which leaves the sentence reading as though the state were the object of the verb.
Phone numbers attract their own errors. Writers borrow the parenthetical form from advertising, (206) 555-0142, or the dotted form from software, 206.555.0142, and both look foreign in edited prose. The house form is hyphens throughout. A related slip is dropping the area code when the audience is mixed, which forces readers outside the region to guess. Finally, writers sometimes begin a sentence with a phone number or a street number, which is awkward but not fatal; the better move is to recast so the number sits inside the sentence, where it reads naturally and keeps its figures.
4 Applying the rule on deadline
On deadline, work from the outside in. First, find every state name and ask whether it is running text or a list form. If it is running text, spell it out and check for the comma pair. If it is a dateline, a table, a list, or a short-form identification, use the standard abbreviation and make sure it matches the others in the same block. Second, scan every phone number and confirm three things: hyphens, an area code unless the audience is purely local, and no stray parentheses or periods. Third, check street addresses for figures in the building number and a consistent treatment of the street-type word.
A quick pass with the search function catches most of this. Search for periods between digits, which flags dotted phone numbers; search for open parentheses followed by digits, which flags the advertising form; search for the common state abbreviations in running text. When you find one, fix it and keep moving. The goal is not to memorize every abbreviation but to recognize the two or three shapes that recur, because those are the ones that reach print. If a form is genuinely ambiguous and the clock is short, choose the spelled-out version in running text, since it is never wrong and rarely awkward.
5 Legitimate exceptions
The rule bends in a few places, and knowing them keeps you from overcorrecting. Datelines are the clearest exception: they use the standard abbreviation, as in AUSTIN, Texas, because the form is a label rather than a sentence. Tables, charts, lists, and mailing addresses also take abbreviations, since space is tight and the reader is scanning rather than reading. Short-form identifications follow the same logic: a second reference to Sacramento, Calif., is acceptable when the full name has already appeared and the abbreviation keeps the sentence from bogging down.
Street numbers are figures in nearly every case, but the number one is the traditional exception: One Main St. reads better than 1 Main St. in formal prose, though either is defensible if the publication is consistent. Phone numbers are always numerals, even at the start of a sentence, because spelling them out would be unreadable; the better fix is to recast the sentence so the number does not lead. Finally, when a state name is part of an organization's formal name or a place name that has no separate city, the comma pair may not apply, as in the state of Texas or a reference to New England. Use judgment, and when in doubt, follow the form the reader will parse fastest.
6 A worked example from the copy desk
A draft arrives with this sentence: The office is at 1 Market Plaza in San Francisco, Calif. and the main line is (415) 555-0199. Three things need attention. The state abbreviation is wrong for running text, so Calif. becomes California. The comma pair is incomplete, so a comma goes after California. The phone number takes hyphens and no parentheses, so it becomes 415-555-0199. The street number stays as One, since the formal spelling is preferred for the number one, and the street-type word is already correct.
The edited sentence reads: The office is at One Market Plaza in San Francisco, California, and the main line is 415-555-0199. Notice what changed and what did not. The facts are identical; only the forms moved. That is the whole point of the rule. A reader who wants to call the office can now dial without translating punctuation, and a reader who wants to find the building can read the address without stumbling over an abbreviation that belongs in a dateline. The desk did not add information or remove it; it removed friction. That is the standard to apply on every pass, whether the piece is a feature, a brief, or a caption under a photograph.
7 Quick reference and related rules
Keep the core forms in mind: spell out states in running text, abbreviate them in datelines, lists, tables, and short-form identifications; use figures for street numbers except One; punctuate phone numbers with hyphens and include the area code unless the audience is purely local; set off a state name with commas on both sides when it follows a city. Related rules follow the same instinct for clarity. Use figures for addresses, ages, percentages, and scores, but spell out numbers at the start of a sentence unless the number is a year or a phone number that cannot be recast. Use commas to separate the elements of a full address, and use the abbreviation ext. for extensions after a comma.
Two habits keep the desk clean. First, read addresses and phone numbers aloud; if the punctuation forces a pause that the spoken form does not have, the punctuation is wrong. Second, check the block, not just the line. A list of ten offices should use one state form throughout, and a story that mentions three phone numbers should punctuate all three the same way. Style is a promise to the reader that the same fact will look the same every time, and addresses, phone numbers, and state names are where that promise is easiest to keep and most noticeable to break.