USA - Union League Club. New York - Union League Club. New York. The club dates its founding from February 6, 1863, during the Civil War. Tensions were running high in New York City at the time, because much of the city's governing class, as well as its large Irish immigrant population, bitterly opposed the war and were eager to reach some kind of accommodation with the Confederate States of America. Thus, pro-Union men chose to form their own club, with the twin goals of cultivating a profound national devotion and to strengthen a love and respect for the Union.. Part of Box 160 Modern New York, Boswell collection.