Where was the Texas MHMR Equestrian Center?

My memory’s hazy on this, but 25+ years ago, driving north on 183 around 620 (I think), there was a small sign (on a gate?) that said something to the effect of Property of Texas MHMR Equestrian Center. Anyone remember that? Exactly where was it/what is it now? Just curious about an old memory 🙂

I’m pretty sure this was before 183 was turned into an elevated freeway. But it’s possible that it was a freeway, but the sign I saw was north of where the freeway ends.