Spanish exploration and activity in the area dated from 1519 through 1821, when Mexico won its independence. In 1828, James McGloin and John McMullen received a Mexican land grant here, to which they brought Irish colonists. The county was created in 1836 and named for St. Patrick, Patron Saint of Ireland. It was organized in 1837, with San Patricio as county seat. The county's southern boundary, the Nueces River, played a major role in events leading to the war with Mexico from 1846 to 1848, including the crossing of the river by Zachary Taylor's army, which had traveled across the county. The county seat was moved to Sinton in 1893.