This paper investigates income transmission dynamics in the United States by providing estimates for intergenerational mobility-- the degree to which a parent's socioeconomic status affects that of their dependents. Using data from the University of Minnesota's Integrated Public Use Microdata Series project (IPUMS), we calculate mobility estimates for Americans born in 1910 and 1980 using county level data. We find that across time, population subset, and model specification, there is strong evidence of spatial dependence in the data. This implies that traditional OLS model specifications used to estimate intergenerational mobility are not appropriate and instead, spatial econometric models should be employed. We also offer further support for an overall decrease in U.S. mobility over time and relatively lower levels of mobility for racial minorities compared to that of whites. Additionally, we discuss the discrepancies in intergenerational mobility across gender lines by examining the relatively unexplored role of women in income transmission relationships.