San Juan County, New Mexico (Extinct)
The original San Juan was a county of New Mexico from 1861 to 1862. Later a different county was created with the same name, which exists to the present. Look for records of San Juan county (extinct) in the Taos county offices.
12 Jan 1861 - SAN JUAN county (original, extinct) created by New Mexico Territory from TAOS county, New Mexico. It stretched west to the California border, including lands in present day Arizona and Nevada. 
- N.M. Terr. Laws 1860-1861, 10th assy. /p. 16
- N.M. Terr. Laws 1861-1862, 11th assy. /p. 16