The USA was the key country of the Seven Countries Study during the first 25 years of the study, with its leadership at the university of Minnesota. Ancel Keys gave the study its scope, design, impetus, and direction. He and his Minnesota colleagues coordinated the program from the Laboratory of Physiological Hygiene in Minneapolis and produced three monographs on the baseline findings and on the five- and ten-year results.
The US railroad cohort differed from the others of the SCS as an industrial worker cohort study initiated the year before the main SCS, with its survey methods applied in the international cohorts. The U.S. cohort consisted of men in the rail industry working along rail lines covering the northwest quadrant of the U.S. and representing occupations of contrasting work activity.