San Antonio, NM
If you are visiting the Bosque Del Apache wildlife reserve, there is a free spot to camp nearby. The site is called the San Antonio Riverine Park. It’s State Land along the Rio Grande right outside of San Antonio. There are no bathrooms, water, trash cans but there are some picnic tables. The main parking area is very noisy as it’s so close to the highway and freight trains come through every couple of hours. But it works if you just want a free campsite.
For more information, you may read this article below:
https://www.tophorsetrails.com/blog/articles/socorro-county-san-antonio-riverine-park-is-a-popular-destination