The TN category arose from the North American Free Trade Agreement (NAFTA). Individuals from Canada or Mexico must qualify under one of the occupations listed in the treaty. Some of the professions listed include engineers, architects, accountants, economists, computer systems analysts, foresters, graphic designers, mathematicians, research assistants, and scientific technicians/technologists. A Canadian may apply at an international airport or border post for TN status; however, Mexicans must first obtain a visa from a U.S. consulate. TN status is approved for one year, and may be extended by the CIS in one‑year increments.