Hidalgo County is the southernmost county of the U.S. state of New Mexico. As of the 2010 census, the population was 4,894. The county seat and largest city is Lordsburg. A bill creating Hidalgo from the southern part of Grant County was passed on February 25, 1919, taking effect at the beginning of 1920. The county was named for the town north of Mexico City where the Treaty of Guadalupe Hidalgo was signed, which in turn was named for Miguel Hidalgo y Costilla, the priest who is known as the "Father of Mexican Independence".