The McMullen-McGloin colony was founded in 1828 by John McMullen and James McGloin after an empresario contract originally granted to John G. Purnell and Benjamin D. Lovell was relinquished. The contract called for settling 200 families on the left bank of the Nueces River above the coastal reserve. In the summer of 1829 McMullen and McGloin went to New York to recruit colonists. They targeted recently arrived Irish immigrants who were not yet established, and by means of interviews and advertisements they found several hundred willing colonists. The first settlers traveled in two groups aboard the Albion and New Packet. Their intended destination was the port of Copano, but the captain of the Albion became disoriented and landed his passengers in Matagorda instead. The groups were eventually reunited and marched inland, where they found shelter at the abandoned mission at Refugio. A second contingent of colonists arrived at Copano aboard the Albion in December 1829 and the third in March 1830. A few of the newly arrived settlers remained in Copano, but the remainder joined the first group in Refugio. Toward the end of 1830 most trekked westward to the Nueces River, where their lands were to be assigned. They congregated near the Santa Margarita Crossing, while the Mexican government official, José Antonio Saucedo, assigned their land. William O'Docharty, one of the colonists, surveyed the allotments.
In October 1831 the colonists laid out a town on the east bank of the Nueces, which they called San Patricio de Hibernia, or St. Patrick of Ireland, for the patron saint of their homeland. In 1833 the schooner Messenger, loaded with additional colonists, arrived at the mouth of Copano Bay, but the captain refused to enter the bay because of bad weather and sailed to New Orleans, where he offloaded his passengers. A few of this group eventually traveled overland to San Patricio, but a number of them succumbed to a cholera epidemic. The original contract, calling for 200 families, was considered suspended by the Law of April 6, 1830, but in 1834 the empresarios secured a four-year extension, and by the outbreak of the Texas Revolution a total of eighty-four titles had been issued. In May 1834 the Messenger brought an additional load of colonists to Copano, and by the eve of the revolution San Patricio was a thriving settlement with a population of nearly 500. Mexican officials, however, were slow to confirm many of the land titles, and a small number of settlers joined the nearby Power and Hewetson colony in protest. Most of the colonists were captured during the revolution and held in Matamoros until after the battle of San Jacinto, when they returned to their homes. All of the land titles issued by the commissioner, José María Balmaceda, were subsequently recognized by the Republic of Texas. Descendents of some of the original colonists still live in the area.