Today there are over 40 million immigrants living in the United States, most of whom come seeking work to improve their earnings and living conditions. Depending on their education and skills, their social networks, government regulations, and other factors, immigrant groups tend to concentrate in specific sectors of the labor market. The articles in this issue of RSF, edited by sociologist Susan Eckstein and economist Giovanni Peri, explore how new immigrant groups navigate the opportunities and constraints presented by various niches in the labor market and how they influence the economic and social fabric of American society. Several articles survey the history of immigrant labor market niches and how they have affected local economies. Siobhan O'Keefe and Sarah Quincy investigate a labor niche--farming--created by Russian Jews in rural New Jersey in the nineteenth century that revitalized local markets and reduced the outmigration of natives from the area. Zai Liang and Bo Zhou study the occupational niches held by Chinese immigrants from the turn of the century to present day. They show that restaurants have historically provided, and continue to provide, a major source of employment for low-skilled Chinese immigrants and that these immigrants tend to use new job-finding services such as employment agencies and internet advertising. These services have also allowed Chinese-owned restaurants to expand into new geographical locations. Other contributors analyze the divisions between high and low-skill labor market niches. In his ethnographic study of restaurants in Los Angeles, Eli Wilson finds that Mexican immigrants primarily work "back of the house" jobs performing low-wage manual labor with few opportunities for advancement, while English-speaking whites hold higher-paid "front of the house" jobs interacting with customers. However, bilingual second-generation Latinos are often able to bridge these two roles, incre