Reference

Texas API county codes

Every Texas API well number starts with 42, the state code. The next three digits are the county code, one of the 254 listed below, so a number beginning 42-001 belongs to a well in Anderson County.

To decode a whole number, including the sidetrack and completion digits, paste it into the API well number decoder.

How to read a Texas API number

42State: Texas
001County: Anderson
12345Well, unique within the county

The first ten digits identify one well. Two more digits can follow for a sidetrack, and two after that for a later completion. The county is the one where the well starts at the surface, so a horizontal well that crosses a county line keeps its surface county's code. A few state regulators assign the producing county instead, so the state record is the final word on a well near a boundary.

All 254 Texas counties

County code County API numbers start
001 Anderson 42-001-
003 Andrews 42-003-
005 Angelina 42-005-
007 Aransas 42-007-
009 Archer 42-009-
011 Armstrong 42-011-
013 Atascosa 42-013-
015 Austin 42-015-
017 Bailey 42-017-
019 Bandera 42-019-
021 Bastrop 42-021-
023 Baylor 42-023-
025 Bee 42-025-
027 Bell 42-027-
029 Bexar 42-029-
031 Blanco 42-031-
033 Borden 42-033-
035 Bosque 42-035-
037 Bowie 42-037-
039 Brazoria 42-039-
041 Brazos 42-041-
043 Brewster 42-043-
045 Briscoe 42-045-
047 Brooks 42-047-
049 Brown 42-049-
051 Burleson 42-051-
053 Burnet 42-053-
055 Caldwell 42-055-
057 Calhoun 42-057-
059 Callahan 42-059-
061 Cameron 42-061-
063 Camp 42-063-
065 Carson 42-065-
067 Cass 42-067-
069 Castro 42-069-
071 Chambers 42-071-
073 Cherokee 42-073-
075 Childress 42-075-
077 Clay 42-077-
079 Cochran 42-079-
081 Coke 42-081-
083 Coleman 42-083-
085 Collin 42-085-
087 Collingsworth 42-087-
089 Colorado 42-089-
091 Comal 42-091-
093 Comanche 42-093-
095 Concho 42-095-
097 Cooke 42-097-
099 Coryell 42-099-
101 Cottle 42-101-
103 Crane 42-103-
105 Crockett 42-105-
107 Crosby 42-107-
109 Culberson 42-109-
111 Dallam 42-111-
113 Dallas 42-113-
115 Dawson 42-115-
117 Deaf Smith 42-117-
119 Delta 42-119-
121 Denton 42-121-
123 DeWitt 42-123-
125 Dickens 42-125-
127 Dimmit 42-127-
129 Donley 42-129-
131 Duval 42-131-
133 Eastland 42-133-
135 Ector 42-135-
137 Edwards 42-137-
139 Ellis 42-139-
141 El Paso 42-141-
143 Erath 42-143-
145 Falls 42-145-
147 Fannin 42-147-
149 Fayette 42-149-
151 Fisher 42-151-
153 Floyd 42-153-
155 Foard 42-155-
157 Fort Bend 42-157-
159 Franklin 42-159-
161 Freestone 42-161-
163 Frio 42-163-
165 Gaines 42-165-
167 Galveston 42-167-
169 Garza 42-169-
171 Gillespie 42-171-
173 Glasscock 42-173-
175 Goliad 42-175-
177 Gonzales 42-177-
179 Gray 42-179-
181 Grayson 42-181-
183 Gregg 42-183-
185 Grimes 42-185-
187 Guadalupe 42-187-
189 Hale 42-189-
191 Hall 42-191-
193 Hamilton 42-193-
195 Hansford 42-195-
197 Hardeman 42-197-
199 Hardin 42-199-
201 Harris 42-201-
203 Harrison 42-203-
205 Hartley 42-205-
207 Haskell 42-207-
209 Hays 42-209-
211 Hemphill 42-211-
213 Henderson 42-213-
215 Hidalgo 42-215-
217 Hill 42-217-
219 Hockley 42-219-
221 Hood 42-221-
223 Hopkins 42-223-
225 Houston 42-225-
227 Howard 42-227-
229 Hudspeth 42-229-
231 Hunt 42-231-
233 Hutchinson 42-233-
235 Irion 42-235-
237 Jack 42-237-
239 Jackson 42-239-
241 Jasper 42-241-
243 Jeff Davis 42-243-
245 Jefferson 42-245-
247 Jim Hogg 42-247-
249 Jim Wells 42-249-
251 Johnson 42-251-
253 Jones 42-253-
255 Karnes 42-255-
257 Kaufman 42-257-
259 Kendall 42-259-
261 Kenedy 42-261-
263 Kent 42-263-
265 Kerr 42-265-
267 Kimble 42-267-
269 King 42-269-
271 Kinney 42-271-
273 Kleberg 42-273-
275 Knox 42-275-
277 Lamar 42-277-
279 Lamb 42-279-
281 Lampasas 42-281-
283 La Salle 42-283-
285 Lavaca 42-285-
287 Lee 42-287-
289 Leon 42-289-
291 Liberty 42-291-
293 Limestone 42-293-
295 Lipscomb 42-295-
297 Live Oak 42-297-
299 Llano 42-299-
301 Loving 42-301-
303 Lubbock 42-303-
305 Lynn 42-305-
307 McCulloch 42-307-
309 McLennan 42-309-
311 McMullen 42-311-
313 Madison 42-313-
315 Marion 42-315-
317 Martin 42-317-
319 Mason 42-319-
321 Matagorda 42-321-
323 Maverick 42-323-
325 Medina 42-325-
327 Menard 42-327-
329 Midland 42-329-
331 Milam 42-331-
333 Mills 42-333-
335 Mitchell 42-335-
337 Montague 42-337-
339 Montgomery 42-339-
341 Moore 42-341-
343 Morris 42-343-
345 Motley 42-345-
347 Nacogdoches 42-347-
349 Navarro 42-349-
351 Newton 42-351-
353 Nolan 42-353-
355 Nueces 42-355-
357 Ochiltree 42-357-
359 Oldham 42-359-
361 Orange 42-361-
363 Palo Pinto 42-363-
365 Panola 42-365-
367 Parker 42-367-
369 Parmer 42-369-
371 Pecos 42-371-
373 Polk 42-373-
375 Potter 42-375-
377 Presidio 42-377-
379 Rains 42-379-
381 Randall 42-381-
383 Reagan 42-383-
385 Real 42-385-
387 Red River 42-387-
389 Reeves 42-389-
391 Refugio 42-391-
393 Roberts 42-393-
395 Robertson 42-395-
397 Rockwall 42-397-
399 Runnels 42-399-
401 Rusk 42-401-
403 Sabine 42-403-
405 San Augustine 42-405-
407 San Jacinto 42-407-
409 San Patricio 42-409-
411 San Saba 42-411-
413 Schleicher 42-413-
415 Scurry 42-415-
417 Shackelford 42-417-
419 Shelby 42-419-
421 Sherman 42-421-
423 Smith 42-423-
425 Somervell 42-425-
427 Starr 42-427-
429 Stephens 42-429-
431 Sterling 42-431-
433 Stonewall 42-433-
435 Sutton 42-435-
437 Swisher 42-437-
439 Tarrant 42-439-
441 Taylor 42-441-
443 Terrell 42-443-
445 Terry 42-445-
447 Throckmorton 42-447-
449 Titus 42-449-
451 Tom Green 42-451-
453 Travis 42-453-
455 Trinity 42-455-
457 Tyler 42-457-
459 Upshur 42-459-
461 Upton 42-461-
463 Uvalde 42-463-
465 Val Verde 42-465-
467 Van Zandt 42-467-
469 Victoria 42-469-
471 Walker 42-471-
473 Waller 42-473-
475 Ward 42-475-
477 Washington 42-477-
479 Webb 42-479-
481 Wharton 42-481-
483 Wheeler 42-483-
485 Wichita 42-485-
487 Wilbarger 42-487-
489 Willacy 42-489-
491 Williamson 42-491-
493 Wilson 42-493-
495 Winkler 42-495-
497 Wise 42-497-
499 Wood 42-499-
501 Yoakum 42-501-
503 Young 42-503-
505 Zapata 42-505-
507 Zavala 42-507-

County names are the US Census names for these codes. The API standard does not promise the two match, so we checked them against state well records. Across 35 states, where this table names a county it matched the one the agency recorded on 85,091 of 85,100 wells. Offshore state and federal waters use their own pseudo-county codes, which are not listed here.

Finding the well itself

The API number stops at the county. It does not hold the well's coordinates, lease, survey section or operator. Those sit in the well record, which you find by searching the full number in the state agency's system. In Texas that is the RRC wellbore query, run by the Texas Railroad Commission (RRC).

For what the Texas public records hold in total, see the Texas oil and gas data summary.

Frequently asked questions

What is the API state code for Texas?

42. API state codes run alphabetically from 01 for Alabama to 49 for Wyoming, then 50 for Alaska and 51 for Hawaii. They are not the Census FIPS state codes, which is a common source of wrong lookups.

How do I find the county from a Texas API number?

Read digits three to five and find them in the table on this page. In 42-001-12345, the county code is 001, which is Anderson County. If the code is missing from the table, it is usually an offshore area rather than an onshore county.

Does a Texas API number give the well's exact location?

No. The number stops at the county. Coordinates, the lease and the survey location are in the well record held by the state agency, which you search with the full API number.

Every Texas well, on one map

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State codes: American Petroleum Institute Bulletin D12A well numbering standard. County names: US Census county FIPS names, checked against state well records. Reference generated .

How to cite this page

Sources: American Petroleum Institute Bulletin D12A well numbering standard; US Census county FIPS codes.

TetraSoft. (2026). Texas API county codes. Reference generated 2026-09-24. https://tetrasoftco.com/tools/api-county-codes/texas/