How persistent are economic gaps across ethnicities? The convergence of ethnic gaps through the third generation of immigrants is difficult to measure because few datasets include grandparental birthplace. I overcome this limitation with a new three-generational dataset that links immigrant grandfathers in 1880 to their grandsons in 1940. I find that the persistence of ethnic gaps in occupational income is 2.5 times stronger than predicted by a standard grandfather-grandson elasticity. While part of the discrepancy is due to measurement error attenuating the grandfather-grandson elasticity, mechanisms related to geography also partially explain the stronger persistence of ethnic occupational differentials. (JEL J15, J22, J31, J51)