Born in Virginia, J. Alfonso DeLaunay was the son of a Revolutionary War veteran and studied law before moving to Tampa in 1848. He worked as the manager of the Palmer House Hotel and became active in local politics. DeLaunay also served as Tampa's Postmaster from 1852 through 1860. He married Victoria Montes de Ocea, daughter of Don Juan Montes de Ocea, a Spanish man who settled at Spanishtown Creek in Hyde Park.
On December 6, 1856, DeLaunay won a special election to complete the remainder of Mayor Lancaster's term of office. DeLaunay served as mayor for slightly over two months during which he attempted to manage the influx of local settlers coming into Tampa to escape attacks by the Seminoles during the Third Seminole War (1855-1858) and the State Legislature's demand that Tampa supply more recruits for the war. Concurrently, DeLaunay guided the transition of the city's administration to conform to the procedures established by the Legislative Act of December 15, 1855.
After losing to Dr. Branch in the next election, DeLaunay returned to his position as Postmaster of Tampa. In 1858, he also became editor for a local newspaper, The Florida Peninsular, but resigned in early 1860, and founded the Sunny South newspaper with his brother. The first issue of this newspaper appeared on January 29, 1861. A strong supporter of secession, DeLaunay served as a Hillsborough County delegate to the Florida Convention which voted overwhelmingly for secession. In early 1861, the Confederate government appointed DeLaunay as Postmaster and Deputy Inspector of Customs for the Port of Tampa, and he served in both capacities throughout the Civil War. The publication of his newspaper, Sunny South, stopped shortly after the outbreak of war and the printing presses and other related equipment were moved to the interior of Florida to prevent their confiscation by Union troops.
In April of 1861, the Confederate government appointed DeLaunay as Confederate States Postmaster, and Deputy Inspector of Customs for the Port of Tampa. He served as a private in the Confederate Army, and was mustered out on April 26, 1865. After the war, he returned to Tampa.