In the present dissertation, we study the United States’ domestic trade and domesticmigration with special focus on Politics, Foreign Import and Size. This study sheds light on the literature of International Economics, Regional Economics, and Development Economics. In Chapter 1, using a Gravity model for trade between the U.S. states and employing CFS data of the year 1993 - 2017, we find that politically and economically similar states trade more among themselves. We use three different definitions of political similarity based on election outcomes, and they all give similar results. For economic similarities, we follow the literature on Linder’s hypothesis. In Chapter 2, by using the same CFS data and Gravity model which we have used in Chapter 1, we analyze the impact of foreign imports by the States on their domestic exports. We find fairly strong support for our hypothesis that foreign imports promote domestic exports. We carry out a series of robustness checks, and the qualitative results remain the same. Chapter 3 investigates the impact of size on the U.S. inter-state migration over the period of 1998-2017 employing structural gravity model of migration. We use population, GDP and Land area as a proxy to measure the size of the states. We find that people are moving from big states to small states. We find that the American’s are moving from big states to small states. We also find that increase in income tax as a proportion of population in U.S. states, positively affect the interstate migration in the origin state but negatively affect the destination state.