In the first half of the 19th century, the North End experienced a significant amount of commercial development. This activity was concentrated on Commercial, Fulton, and Lewis Streets. During this time the neighborhood also developed a red-light district, known as the Black Sea. By the late 1840s, living conditions in the crowded North End were among the worst in the city. Successive waves of immigrants came to Boston and settled in the neighborhood, beginning with the Irish and continuing with Eastern European Jews and Italians. Boston as a whole was prosperous, however, and the wealthy residents of the North End moved to newer, more fashionable neighborhoods such as Beacon Hill.