There are 8 US Post Offices in Eddy County serving a total of 53,634 residents equating to 6,704 residents per post office. It's estimated that approximately 85,606 packages are handled across the 8 county post offices annually. Eddy County is a county located in the U.S. state of New Mexico. As of the 2010 census, the population was 53,829. Its county seat and largest city is Carlsbad. The county was created in 1891 and later organized in 1891. It is north of the Texas state line. Eddy County comprises the Carlsbad-Artesia, NM Micropolitan Statistical Area. Carlsbad Caverns National Park is located in this county. Eddy County is the location of the Waste Isolation Pilot Plant.