Was economic mobility high during the first half of the twentieth century in the United States? I combine two historical data sources to estimate intergenerational income mobility between 1915 and 1940. I match fathers from the Iowa State Census of 1915 to their sons in the 1940 Federal Census, the first state and federal censuses with data on income and years of education. In my sample of fathers and sons, I estimate a lower intergenerational elasticity of income than is found in modern studies of the United States, suggesting higher levels of income mobility. Income mobility measured with relative income ranks also show higher mobility historically. Intergenerational mobility of education is higher in my sample than in modern measures as well. I find sons in rural counties in 1915 to have more mobility of both income and education than urban sons. Lacking data on income, past studies of historical intergenerational mobility have relied on occupation transition data for fathers and sons to measure mobility. When I compute standard measures of occupational mobility for my sample, I find levels of mobility between 1915 and 1940 to be larger than modern estimates, confirming the higher mobility I find in income measures. This suggests that the standard estimates of historical occupational mobility may be accurate substitutes for measures of income mobility when income data does not exist.