 Author Beatrice Krier claims that Ulao is a corruption of the Spanish word "Ulloa", which was probably chosen because of a local veteran named Weber, who had participated in the Siege of Veracruz in March 1847 during the Mexican–American War, when U.S. troops under the command of Winfield Scott surrounded and overran the castle of San Juan de Ulúa, which itself was named for the Spanish explorer Francisco de Ulloa, who had navigated the western coast of Mexico as part of the 1539 expedition of the conquistador Hernán Cortés.Other explanations claim that it was named after a Native American leader, that it's a corruption of an American general's French Huguenot name, or that the whistles of the engines of the Northwestern Railroad's pilot engines screamed something akin to "YOU LAY O" as they approached the community's depot.Ulao's founder was an investor named James T. Gifford, who also founded the city of Elgin, Illinois.