N.M. Stat. § 4-23-1
That there be and is hereby created a county, to be known as and called the county of Sandoval, out of that portion of the territory of New Mexico included within the following boundaries, to wit:
beginning at a point three miles north of the southwest corner of township twenty-three north, of range seven west of the New Mexico principal meridian, according to the public land surveys of the United States, and running thence east along the line three miles north of the line between townships twenty-two and twenty-three north to the said principal meridian, which line shall form a part of the southern boundary of Rio Arriba county; thence south along said principal meridian to the fifth standard parallel north; thence east along said fifth standard parallel north to the range line between ranges six and seven east at the northwest corner of township twenty north in range seven east; thence south along said range line between ranges six and seven east; the same being the western boundary of Santa Fe county, to the southeast corner of township twelve north in range six east of said principal meridian; thence west along the township line between townships eleven and twelve north, said line being the northern boundary of Bernalillo county, to the boundary line of Valencia county at the northwestern corner of Bernalillo county; thence in a northwesterly direction along the boundary line of Valencia county to the third standard parallel north; thence west along said third standard parallel north, to the southeastern corner of McKinley county; thence north and along the eastern boundary line of McKinley county to the fifth standard parallel north at the southwest [northwest] corner of township twenty-one [twenty] north in range four west; thence west along said fifth standard parallel north to the southeast corner of San Juan county at the southwest corner of township twenty-one north in range seven west, and thence north along the range line between ranges seven and eight west, said line being the easterly boundary of San Juan county, to the place of beginning.
NMS § 4-23-1