When One magazine published its first issue in January 1953, it became the first widely distributed gay publication in the United States. Created by One Inc., the gay rights organization founded the year before, the pioneering magazine is celebrating its trailblazing pages and its influential 14-year run with a new exhibit in Los Angeles. Starting Sunday at the Advocate & Gochis Galleries at the Los Angeles LGBT Center, “ONE Magazine at Seventy” offers visitors a chance to dig into the brainchild of writer Jim Kepner and activist W. Dorr Legg. The exhibit kicks off the inaugural “Circa: Queer Histories Festival,” a monthlong celebration of the seven decades of the organization that first founded the storied magazine.