Irish immigrants settled this area as part of the John McMullen and James McGloin Mexican land grant. Located on the sulphur tributary of the Nueces River, this site was known as "on the sulphur". Live Oak County was organized in 1856 and "Oakville" was named county seat. Thomas Wilson gave 640 acres for the townsite stipulating that separate square be marked as public, graveyard, church, and school squares. Oakville grew as stores, two hotels, a livery stable, a school, and two churches were established. The Oakville post office was established May 11, 1857, with Joshua Hinton as the first postmaster. The mail came four times a week on stagecoaches traveling from San Antonio to Corpus Christi and on to Brownsville.
By 1879 the San Antonio-Corpus Christi stage left both ends of the line six days a week. Stage travel became less popular with the arrival of the railroad. When the San Antonio, Uvalde & Gulf railroad bypassed Oakville in 1913, the town began to decline. The county seat was relocated in 1919 at George West. In 1966 the Oakville Post Office was designated as a rural branch of the Three Rivers Post Office and continues to serve the community.