Southern New Mexico and Arizona in the Civil War: Confederate Territory

Yes—They Were Confederate (Briefly)

In 1861–1862, the southern halves of both the New Mexico Territory and the newly declared Confederate Territory of Arizona aligned with the Confederacy.

How It Happened

1. March 1861: Secession conventions in Mesilla (NM) and Tucson (AZ) voted to join CSA.
2. August 1861: Lt. Col. John Baylor (2nd Texas Mounted Rifles) occupied Mesilla, declared Confederate Territory of Arizona (all NM Territory south of 34°N), named himself governor.
3. Feb 1862: Confederate Congress officially recognized Arizona Territory (capital: Mesilla, then Tucson).
4. Boundary: Ran along 34th parallel — roughly south of Tucson. North = Union NM Territory; South = Confederate AZ Territory.

Military Campaign

• Sibley's New Mexico Campaign (1862): Brig. Gen. Henry Sibley led 2,500 Texans north along Rio Grande.
• Valverde (Feb 1862): Confederate victory; Union retreated to Fort Craig.
• Albuquerque & Santa Fe occupied (Mar 1862).
• Glorieta Pass (Mar 26–28, 1862): "Gettysburg of the West" — Union (Colorado volunteers + NM militia) destroyed Confederate supply train. Sibley retreated.
• By July 1862: All Confederate forces withdrawn to Texas. Union control restored.

Why It Mattered

• Confederacy wanted Colorado gold, California ports, Pacific access.
• Union victory secured the Southwest, enabled California Column to march east (securing AZ/NM for Union).
• Apache & Navajo wars intensified during power vacuum.

Post-War

• 1863: US Congress created Arizona Territory (different boundaries: north-south split, not east-west).
• 1912: Both admitted as states (NM Jan 6, AZ Feb 14).

Bottom Line

Southern NM & AZ were de facto and de jure Confederate for ~6 months (1861–62). The border ran south of Tucson. Union victory at Glorieta Pass ended it. The modern states owe their boundaries to post-war Republican Congress, not Confederate lines.