| County |
Created |
Parent County |
County Seat |
| Bernalillo County |
1852 |
Original County
|
Albuquerque, Bernalillo County, New Mexico |
| Catron County |
1887 |
Socorro County |
Reserve, Catron County, New Mexico |
| Chavez County |
1921 |
Lincoln County |
Roswell, Chavez County, New Mexico |
| Cibola County |
1981 |
Valencia County |
Grants, Cibola County, New Mexico |
| Colfax County |
1869 |
Taos County |
Raton, Colfax County, New Mexico |
| Curry County |
1909 |
Quay, Roosevelt Counties
|
Clovis, Curry County, New Mexico |
| De Baca County |
1909 |
Chaves, Guadalupe, Roosevelt Counties |
Ft. Sumner, De Baca County, New Mexico |
| Dona Anna County |
1852 |
Original County |
Las Cruces, Dona Anna County, New Mexico |
| Eddy County |
1889 |
Original County |
Carlsbad, Eddy County, New Mexico |
| Grant County |
1868 |
Dona Anna County |
Silver City, Grant County, New Mexico |
| Guadalupe County |
1891 |
Lincoln, San Miguel Counties |
Santa Rosa, Guadalupe County, New Mexico |
| Harding County |
1891 |
Mora, Union Counties
|
Mosquero, Harding County, New Mexico |
| Hildago County |
1919 |
Grant County |
Lordsburg, Hildago County, New Mexico |
| Lea County |
1917 |
Chaves, Eddy counties |
Lovington, Lea County, New Mexico |
| Lincoln County |
1869
| Socorro, Dona Ana counties |
Carizozo, Lincoln County, New Mexico |
| Los Alamos County |
1949 |
Sandoval, Santa Fe counties |
Los Alamos, Los Alamos County, New Mexico |
| Luna County |
1901
| Dona Ana, Grant counties |
Deming, Luna County, New Mexico |
| McKinleyCounty |
1899 |
Bernalillo, Valencia, San Juan, Rio Arriba counties |
Gallup, McKinley, County, New Mexico |
| Mora County |
1860
| Taos County |
Mora, Mora County, New Mexico |
| Otero County |
1899 |
Dona Ana, Lincoln, Socorro Counties |
Alamogordo, Otero County, New Mexico |
| Quay County |
1903 |
Guadalupe County |
Tucumcari, Quay County, New Mexico |
| Rio Ariba County |
1852 |
Original County |
Tierra Amarilla, Rio Ariba County, New Mexico |
| Roosevelt County | <
1903 |
Chaves, Guadalupe County |
Portales, Roosevelt County, New Mexico |
| San Juan County |
887 |
Rio Ariba County |
Aztec, San Juan County, New Mexico |
| San Miguel County |
1852 |
Original County |
Las Vegas, San Miguel County, New Mexico |
| Sandoval County |
1903 |
Bernalillo County |
Bernalillo, Sandovall County, New Mexico |
| Santa Ana County |
1844 |
Original County |
Algodones, Santa Ana County, New Mexico |
| Santa Fe County |
1852 |
Original County |
Santa Fe, Santa Fe County, New Mexico |
| Sierra County |
1884 |
Socorro County |
Truth or Consequences formerly Hot Springs, Sierra County, New Mexico |
| Socorro County |
1884 |
Original County |
Socorro, Socorro County, New Mexico |
| Taos County |
1852 |
Original County |
Taos, Taos County, New Mexico |
| Torrence County |
1903 |
Lincoln, San Miguel, Socorro, Santa Fe, Valencia Counties |
Estancia Torrence County, New Mexico |
| Union County |
1893 |
Colfax, Mora, San Miguel Counties |
Clayton, Union County, New Mexico |
| Valencia County |
1852 |
Original County |
Los Lunas, Valencia County, New Mexico |