New Mexico Statutes Chapter 4. Counties § 4-31-1. Original county boundaries

That the county of Union is hereby created out of that portion of the territory of New Mexico lying and being situate within the following metes and bounds, to wit: commencing at a point on the line between the state of Colorado and the territory of New Mexico where the range line between ranges twenty-seven and twenty-eight east crosses said line between the territory of New Mexico and state of Colorado; thence from said point, running south on said range line between ranges twenty-seven and twenty-eight east, to the south line of the county of Mora, in said territory; thence east along the south line of the said county of Mora to the east line of what is known and called the Pablo Montoya grant; thence in a southeasterly direction along the easterly line of the said Pablo Montoya grant to the north line of what is called and known as Baca location number two; thence east along the north line of said Baca location number two to the northeast corner of said Baca location number two; thence south along the east line of said Baca location number two to the southeast corner of said Baca location number two; thence continuing south to the township line between townships eleven and twelve north; thence east along said line between townships eleven and twelve north, to the east line of the territory of New Mexico; thence north on the east line of the territory of New Mexico to the northeast corner of said territory of New Mexico; thence west along the north line of said territory of New Mexico, to the range line, between ranges twenty-seven and twenty-eight east, the point of beginning.