N.M. Stat. § 4-9-1
All that portion of the territory of New Mexico embraced within the following boundaries, to wit: commencing at the corners of townships twenty and twenty-one south, range seven and eight west, which said corners are about four miles northeasterly from Fort Cummings, in Dona Ana county; thence running northerly in a direct line across the summit of the Sierra Mimbres to a point due west of Ojo del Muerto; thence west to the western boundary of the territory; thence south along said boundary to the southwest corner of the territory; thence following the southern boundary of the territory eastwardly to a point on said southern boundary due south of the place of beginning; thence north to the place of beginning, shall form and constitute a new county to be called Grant county.
NMS § 4-9-1