Michael (Miguel) Muldoon, priest, was born around 1780 in the Diocese of Kilmore, County Cavan, Ireland. According to family tradition he was ordained at the Irish College of Seville, Spain, one of several Irish Catholic colleges established on the continent as a result of British penal laws that proscribed the teaching of the Catholic faith in Ireland. He received faculties through the Diocese of Monterrey, Mexico, and served in Texas in 1831–32. He was the only priest appointed to serve non-Hispanic Texas settlers. Muldoon is believed to have arrived in Veracruz in 1821 in the company of Juan O'Donoju, the last Spanish viceroy of Mexico. Stephen F. Austin considered Muldoon sufficiently tolerant to provide for the spiritual needs of the predominantly Protestant colonists whom Austin represented. Colonists who nominally accepted the Catholic faith in order to secure their land, as required by the Mexican government, came to be known as Muldoon Catholics. During Muldoon's brief tenure in Texas, from April 1831 to August 1832, Austin realized that Muldoon's political connections in Mexico could prove useful because he was a close friend of Mexican general Manuel de Mier y Terán. When the general visited Anahuac in November 1831, while Austin was ill in bed in San Felipe, Muldoon kept Austin informed of the nature of Mier's visit. In June 1832 Muldoon offered himself as hostage to free prisoners held by John Davis Bradburn at Anahuac (see ANAHUAC DISTURBANCES), but his offer was not accepted.
In August 1832 Muldoon returned to Mexico. He arrived in Monterrey in September and published a broadside defending the conduct of the Texans and stating that he had traveled to Monterrey to pay his respects to the newly appointed bishop there. There is no record of Muldoon's returning to Texas until after the Texas Revolution. He was residing in Mexico City in 1834 when Austin was imprisoned there on orders of acting president Valentín Gómez Farías. He was the only visitor to the cell where for three months Austin was held incommunicado, and at one point he secured a North American businessman to serve as bondsman for Austin. Although the bond offer was rejected by the government, Muldoon continued to work on behalf of Austin by visiting President Antonio López de Santa Anna at Manga de Clavo. Although Santa Anna eventually intervened in Austin's case, recommending to the court that he be acquitted, Austin was not released until proclamation of a general amnesty law in the summer of 1835.
In 1837 Muldoon helped William H. Wharton escape from a Mexican prison at Matamoros. Although he never returned to Texas in any official capacity, as late as 1839 Father Muldoon performed a wedding in Houston as Catholic vicar general of the Republic of Texas. In April 1839 he appeared in New Orleans, where he offered to serve as an interpreter for Col. Barnard E. Bee, Sr., who was preparing to embark on a diplomatic mission to Mexico. For his unofficial part in this mission, that of proceeding to Mexico City while the official envoys remained in Veracruz, and for his pro-Texan views, Muldoon was imprisoned. Instead of being charged accordingly, however, he was accused of previously having left Mexico without the proper travel documents. By 1842 Muldoon was again in Texas, where he received from Secretary of State Anson Jones a letter recognizing his service to the republic. The tone of the letter suggests a final departure from Texas. Austin had disposed of at least part of the eleven leagues of land in Texas that Muldoon bought in Saltillo in 1831.