DescriptionIn this thesis I study immigrants and immigration policies in the historical and modern United States. This thesis is composed of three chapters concerning the impact of immigrants on the US economy and the labor market performance of immigrants. In the first two chapters, I study the effects of the historical immigration quota system on manufacturing wages, the internal migration of the black population, and industrial development of the manufacturing sector. In Chapter 3, I turn to high-skilled immigrants in the modern US and study the ability of high-skilled immigrants to transfer their foreign human capital to the US and what affects immigrants' human capital transferability. In Chapter 1, I recount the immigration quota system established in the 1920s US and use it as a natural experiment to identify the effects of immigration on the manufacturing wages between 1920 and 1930. The immigration quota system was established in 1921 and permanently in 1924 that severely restricted immigrant inflow from Southern and Eastern Europe while imposing a modest restriction on Western and Northern European immigrants. Hence US regions that historically had received more Eastern and Southern European immigrants experienced a greater decline in the supply of immigrants caused by the quotas. I estimate the number of immigrants excluded from each US region by the quotas as the instrumental variable for the change in the regional immigrant share in this decade. I find that the more immigrants excluded from a US region by the quota system led to a greater decrease in the foreign-born population share and significantly increased the regional manufacturing wage level. In Chapter 2, I use the immigration quota system to examine the effect of immigrants on the labor mobility of the native black population and the adjustments of industrial production in the manufacturing sector. I show a causal relationship between immigration restriction and the Great Migration of the southern black population: a greater decline in the supply of immigrants resulted in a greater inflow of black migrants. Regarding industrial development, I find that a region that experienced a greater decline in immigrant supply had a slower growth of the scale of production and electrification in the manufacturing sector. In Chapter 3, I study the return to human capital of US high-skilled immigrants using the National Survey of College Graduates. I find that high-skilled immigrants can not fully transfer their foreign human capital and have a low return to foreign human capital. STEM immigrants overall have a higher return to foreign experience and to foreign bachelor than non-STEM immigrants. I show that better mastery of English helps non-STEM immigrants transfer more foreign human capital and enjoy a higher return. STEM immigrants transfer more foreign human capital in general than non-STEM immigrants and their transferability of foreign human capital is not significantly affected by English skills probably because STEM-related human capital is less language-specific. I also find that immigrants who originally entered the US with temporary work visas have a slightly higher return to foreign human capital but a lower return to US human capital than immigrants with other entry visas.