In 1940, the Portuguese government approved a massive primary school construction plan that projected a 60 per cent increase in the number of primary schools. Based on the collection of a new dataset, we describe literacy levels in Portugal prior to the plan as well as the plan's strategy regarding the location of schools. We then estimate the causal impact of the increase in the number of schools between 1940 and the early 60s on enrolment and literacy, all at the county level. We conclude the increase in the number of schools was responsible for 80 per cent of the increase in enrolment and 13 per cent of the increase in the literacy rate of the affected cohorts.