MESILLA COUNTY, NM HISTORY AND LOOKUP (EXTINCT COUNTY, 1854-1863)

County History Books

*None Listed

Mesilla County, New Mexico: A Genealogical Overview

Mesilla County was a short-lived, de facto administrative entity that existed only during the American Civil War. Critically for researchers, it was not a legal county of the United States’ New Mexico Territory. Instead, it was the primary judicial district of the Confederate Territory of Arizona, established by military proclamation after Confederate forces occupied the region. Its capital was Mesilla, which was also the legitimate county seat of the much larger Doña Ana County, New Mexico Territory. Its history is brief, turbulent, and tied directly to the Confederate campaign to control the American Southwest. All genealogical research for this period must be conducted within the records of its U.S. counterpart, Doña Ana County.

I. County Formation and Evolution

Understanding that “Mesilla County” was a temporary Confederate jurisdiction overlaid upon an existing U.S. county is essential to locating records.

  • 1861: “County” Formed: Mesilla County was created on August 1, 1861, by a military proclamation from Confederate Lieutenant Colonel John R. Baylor. This followed his capture of U.S. forces at Fort Fillmore and the occupation of the town of Mesilla.
  • Parent Entity: The territory claimed by Mesilla County was carved directly from the southern half of the existing Doña Ana County, New Mexico Territory. At the time, Doña Ana County stretched from the Texas border to the Colorado River, the modern border of California.
  • Dissolution and Successor Jurisdiction: The Confederate government and Mesilla County’s administration collapsed in July 1862 with the arrival of the Union Army’s California Column, which recaptured the territory for the Union. Administrative authority immediately and fully reverted to Doña Ana County, New Mexico Territory. Therefore, Doña Ana County is both the parent and the successor entity, and its records are continuous through this period.
  • Name Origin: The county was named for its capital, the prominent town of La Mesilla (Spanish for “the little tableland”).
  • County Seat History: Mesilla served as the capital of the Confederate Territory of Arizona and the seat of Mesilla County for the duration of its existence. It was the largest and most economically important town in the entire region at the time.

II. Settlement and Early History

  • Early Inhabitants: The region was the traditional homeland of various Apache bands, particularly the Chiricahua and Mescalero Apache, whose raids were a constant feature of life for settlers.
  • Mexican and American Settlement: The town of Mesilla was founded in 1848 by Mexican citizens on what was then the Mexican side of the Rio Grande. The Gadsden Purchase of 1854 officially made the Mesilla Valley part of the United States. The area’s economy was based on agriculture irrigated by the Rio Grande, ranching, and its strategic location as a major hub on the Butterfield Overland Mail route. Pro-Southern sentiment was strong among many of the Anglo-American residents.
  • Key Historical Events:
    • Gadsden Purchase (1854): This treaty finalized the U.S.-Mexico border, placing Mesilla and its surroundings firmly within the New Mexico Territory.
    • Confederate Occupation (July 1861): Lt. Col. John R. Baylor’s invasion from Texas established Confederate control, which lasted for approximately one year.
    • Recapture by the Union (July 1862): The advance of the California Column under General James H. Carleton caused the Confederates to abandon Mesilla and retreat to Texas, effectively ending the existence of the Confederate Territory of Arizona and Mesilla County.

III. Genealogical Records and Resources

This section provides practical information for locating ancestral records. Researchers must look for records under “Doña Ana County,” not “Mesilla County.”

  • County Courthouse (Successor Repository): No separate set of records exists for “Mesilla County.” Any civil records created during the Confederate occupation (deeds, probate cases, etc.) were entered into the existing record books of Doña Ana County. All research for this time and place must be directed to the Doña Ana County Clerk’s Office, now located at 845 N. Motel Blvd, Las Cruces, NM 88007.
  • Vital Records:
    • Birth and Death Records: Civil registration of vital statistics did not exist in New Mexico during the territorial period. All birth (baptism) and death (burial) information must be sought in church records.
    • Marriage Records: The primary source for marriages during this era are the sacramental records of the Catholic Church. The historical parish for the area is the Basilica of San Albino in Mesilla, whose records are invaluable for genealogical research. Some civil marriage records may also be found in the books of the Doña Ana County Clerk.
  • Archives and Libraries:
    • Rio Grande Historical Collections, NMSU Library: Located in Las Cruces, this is the premier archival repository for the history of southern New Mexico. It holds manuscript collections, photographs, and microfilm copies of many Doña Ana County records.
    • New Mexico State Records Center and Archives (NMSRCA): Located in Santa Fe, this archive holds New Mexico territorial papers and microfilm copies of records from all New Mexico counties.
  • Bordering Jurisdictions (of the parent Doña Ana County in 1861):
    • Socorro County, New Mexico Territory (north)
    • State of Texas (east)
    • The Republic of Mexico (south)
    • The western boundary was the Colorado River, bordering California.

Please share any resources you have and will do lookups or links to resources you are aware of. Thanks