Historically a nation of immigrants, the United States is home to nearly 45 million immigrants, who represent 13.7 percent of the total population and play a key role in the economic, civic, and cultural life of the country. The research collected here covers many facets of immigration to the United States, by the numbers and how immigrants fare in the country's classrooms and workplaces, the policies and regulations that shape the admission of new immigrants, the enforcement programs and polices in place at U.S. borders and within the interior, and integration policies and efforts taking place in local communities, in states, and at the federal level.