"US history is characterized by two episodes of mass in-migration, an era of unrestricted migrant arrivals from Europe (1850-1913) and a more recent period of constrained mass migration, primarily from Asia and Latin America (1965-present). Many of the same topics that concern the economics of immigration today – including migrant selection and assimilation and the effect of immigrant arrivals on native workers – were also relevant in the past. We argue that comparing the research findings across these two periods can illuminate contemporary debates. In particular, our reading of the literature suggests that migrant selection, which is primarily positive today, was decidedly mixed in the past, with cases of negative migrant selection from some European sending countries. Changes in migrant selection over time are consistent with rising bureaucratic costs of migration, which may price out the poor, and with growing income inequality in the US, which would attract a higher-skilled set of immigrants. Upon arrival, the average long-term immigrant in the past held a similar set of occupations to the average native worker, and moved up the occupational ladder at the same pace. The pace of economic convergence between immigrants and natives was relatively slow in both the past and the present, with the notable difference that, today, the average immigrant starts out with a larger earnings gap to overcome (although there is substantial variation in initial earnings by sending country). It appears that historical estimates of the effect of immigrant arrivals on native wages are larger than comparable estimates for today, which may be due to the fact that, in the past, immigrants and natives held a similar set of skills. However, comparisons of these magnitudes over time are complicated by methodological differences, and could be improved with a new round of well-identified historical studies on the effect of immigration on labor markets."