The New York Times’ lead editorial in the November 12 paper edition is “The Worst Voter Turnout in 72 Years”. Here is a link to the editorial. The editorial contains a graph, showing turnout back to 1900. The figures are from Professor Michael McDonald, who calculates the number of voters, as a percentage of the number of persons who were eligible to register and vote. In other words, the percentages do not relate to how many registered voters there are, just the potential electorate if everyone did register.
Turnout was low in the 1920’s because women had won the right to register to vote, but many women, initially, did not feel comfortable registering or voting. Turnout was low in 1942 because back then, no one could register into a state without having lived in that state for a year, and a large proportion of the population moved during 1942, into states with factories that started producing armaments, or went overseas because of service in the armed forces.