Abstract: In 1924, The Morton Salt Company began nationwide distribution of iodine-fortified salt. Access to iodine, a key determinant of cognitive ability, rose sharply. We compare outcomes for cohorts exposed in utero to iodized salt with those of slightly older, unexposed cohorts, across states with high versus low iodine deficiency rates prior to salt fortification. Incomes for cohorts who benefited from iodized salt access went up by 3%, with a nearly 8% increase during school-going ages. We find a small but precisely measured decline in educational attainment (-0.04 years), mainly due to decreased schooling in states with blue-collar jobs. Employment rose by 1%, driven by a 2% rise at school-going ages and focused on entry into low-wage jobs. Later in life, exposed cohorts began to shift into self-employment. These results are consistent with a model of schooling choice in which cognitive ability raises both the returns to education as well as the wage at labor force entry, leading to a rise in income and employment but an ambiguous effect on educational attainment.