Dennis Gahagan (born c.1817) was an immigrant in the Mexican Pueblo de San Diego in territorial California, and early settler in the City of San Diego in the new U.S. state of California. History Mexican–American War Dennis Gahagan was born c. 1817 in Ireland. He emigrated to the United States in the early 1840s. He joined the U.S. Army, which was recruiting for the Mexican–American War. He arrived in San Diego by 1849 as a soldier with the First U.S. Artillery (Magruder's Battery). He and his fellow troops fought and patrolled in the Southern California countryside during the war. U.S. territorial period In 1849 Gahagan was elected U.S. Judge of the 1st Instance of the District of San Diego. From 1849 to 1850 Gahagan was an Alcalde (Mayor) of San Diego. References 1850 Census, San Diego, California, p. 273A See also List of pre-statehood Mayors of San Diego, California American judges American military personnel of the Mexican–American War People from San Diego Irish emigrants to the United States (before 1923) 1817 births Year of death missing History of San Diego