TX is Texas. Austin is the capital, Houston is the largest city, and Texas entered the Union on December 29, 1845, as the 28th state.
Why the code is TX
TX belongs to a small family of codes built from the first and last letter of the state name rather than the first two. Maryland gives MD, Kentucky gives KY, Pennsylvania gives PA, and Texas gives TX. Read the name and the code out loud together and the pattern is obvious once you have seen it once.
The reason Texas needed that pattern is Tennessee. Two states start with T, and only one could take the plain opening pair. Tennessee took TN. Texas was left with TE, and TE against TN is one stroke of a pen apart on a hand-addressed envelope, which was the exact problem the October 1963 list was written to eliminate. The Post Office Department was compressing every state to two characters so that city, state and the newly launched ZIP code would fit on one printed line, and any pair that could smudge into another pair was a liability.
The x solved it outright. No other single-word state name contains an x, so TX competes with nothing else in the set of fifty. The letter also survived the switch from the older written form. Before 1963, clerks and printers wrote Tex., keeping the same three consonants that give the modern code its shape, and that spelling still runs in legal citations and newspaper datelines. New Mexico is the only other state whose name carries an x, and its code takes the M instead, leaving the x to Texas alone.
Codes people confuse with TX
| Code | Stands for | Why the mix-up happens |
|---|---|---|
| TN | Tennessee | The one collision that shaped the code. Tennessee holds the T slot that Texas would otherwise have filled, and the two codes differ by a single letter. |
| TE | Not a state code | The instinct is to clip the first syllable, so TE gets written on forms. USPS has never issued it, and mail carrying it is sorted by ZIP code alone. |
| TEX | Texas in sports and citation | Three letters in box scores for the Rangers, and a period at the end for court filings. Neither belongs in the state field of an address. |
| MX | Mexico | Texas holds the longest stretch of the US border with Mexico, and the two codes share the x. On customs paperwork they sit in adjacent fields and get swapped. |
| Tx | Treatment, in medical shorthand | Clinical notes use Tx for treatment and Dx for diagnosis, so searching the two letters alone returns results that have nothing to do with any state. |
Quick facts about Texas
| Capital | Austin |
| Largest city | Houston, which is not the capital, unlike in most large states |
| Region | South, in the South Central group with Oklahoma and Louisiana |
| Statehood | December 29, 1845, the 28th state, after nine years as an independent republic |
| Population band | Over 10 million, second only to California |
| Size | 2nd largest state by area, behind Alaska |
| Time | Central time across nearly all of the state, with the El Paso corner on Mountain time |
Where you will see TX
On mail. Texas ZIP codes run through the 75 to 79 block, so Dallas TX 75201 and Austin TX 78701 both encode the state twice. The El Paso area also uses a small 885 range, a leftover of how the sorting network was drawn.
On paperwork in Spanish. The abbreviation does not change language. A parcel posted in Monterrey to a Houston address is still labelled TX, because the code is a USPS routing token rather than a word. Spanish prose keeps the full name Texas, and Tejas is the older spelling that survives in place names and song titles.
In markets. Texas Instruments trades under the ticker TXN, three letters that borrow the state code and add an N. Ticker symbols and postal codes are separate systems that happen to overlap here.
In crosswords. "Lone Star St." and "Austin's home, briefly" both want TX. Constructors like the x for the same reason the Post Office did.
TX, TN, TEX, all in one grid
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