NULL Of 254 counties in the Lone Star State, Duval County ranks 14th by size (1,795 square miles). Duval County is in Rio Grande Plains Texas. Recent Land Network data includes 1,000 acres of horse farms for sale in Texas's Duval County, which is valued at a combined $169,900. Browse all Duval County horse farms for sale on the Land Network to find the equestrian property that's right for your future needs, whether you're a horse breeder, equestrian business or simply horse lover looking for stable facilities, grooming pens or grazing pasture for your own horses. The most common type of land for sale by combined acreage in Duval County is hunting land.