During 1999, he served as the 62nd Chairman of the Council of State Governments, the youngest and first Hispanic in that organization's 75-year history. During his terms in CSG leadership, the organization strengthened its international ties, admitting several Canadian provinces as international member jurisdictions, co-sponsoring the foundation of the Parliamentary Conference of the Americas, and co-chairing with CSG President and Wisconsin's then-Governor Tommy Thompson a mission to the People's Republic of China, in which he met with Premier Zhū Róngjī. As chairman, McClintock increased the presence of Hispanics in CSG committees and task forces and helped organize CSG's best attended Annual Meeting ever, held in Quebec City, Canada. He also was part of the official delegation that attended the December 14, 1999, ceremonies commemorating the final turnover on December 31, 1999, of the Panama Canal to the Panamanian authorities.