Almost abandoned, now revived but relatively unknown, one of my favourites is the Mungalalu Truscott Airbase in northern Australia, used during WWII for long range bombing of Japanese oil wells and depots in SE Asia.
Another in the north is Gorrie Airfield from WWII; now used as a boondocking/free-camping spot. We camped on it driving south from Katherine last month - great, flat area with lots of room for people to spread out. There would've been 10-20 camping rigs set up.
One guy I worked with started a glider club. Turns out they needed a runway. So they made one out of an old farmers field. No real runway just an empty field cut low and a small shack at the end of the run way to fix things. "I am going to name it an international something, not sure what". Few years later I asked him if they gave him his international name. They had! So this little random field is an 'international' airport.
Aw sorry dude it was like 20 years ago at this point. I do remember it started with an I and it was in the middle of North Carolina near Advance. They may have closed it since then.
Could it have been the Northbrook International Ultraport Ultralight Airport? It gets pretty close to your description: one grass runway, listed as privately owned by a James K. Peeler and nestled in underneath the Charlotte-Douglas International Airport's airspace in North Carolina.
https://en.wikipedia.org/wiki/Mungalalu_Truscott_Airbase
Still home to WWII era (well, 1946 to 1951) Grumman G-73 Mallard air boats.
https://en.wikipedia.org/wiki/Grumman_G-73_Mallard
https://www.youtube.com/watch?v=eqMQWO5ffTA