More than half of the early European immigrants had arrived as indentured servants, who worked for a period of years without wages in exchange for their passage to and upkeep in America. Immigrants to colonial America were welcomed because of an acute need for labor. After independence, only "free, white persons" were eligible to become citizens. Citizenship was not extended to persons of African descent until the passage of the 14th amendment to the Constitution in 1868.
From 1815 to the start of the Civil War in 1861, five million people moved to the United States, about half from the British Isles, including Ireland. Most sailing ships that brought Europeans across the Atlantic Ocean were overcrowded, poorly ventilated, and without sanitation. At the peak of Irish immigration in the 1840s, about 25% percent of those in steerage died during the voyage. Once in the United States, the Irish faced discrimination because they were Catholic and impoverished. After the War with Mexico ended in 1848 with the Treaty of Guadalupe Hidalgo, Mexico acknowledged the 1845 annexation of Texas and ceded to the United States a huge expanse of land that included the present- day states of California, New Mexico, Nevada, Utah and parts of Arizona, Colorado, and Wyoming. The 75,000 Spanish-speaking residents of this southwestern territory became citizens of the United States without having immigrated here. Relatives on both sides of the border with Mexico continued to travel back and forth between the two countries to visit and to work. .
Prior to the Civil War, three-quarters of the immigrants coming to the United States arrived at the Eastern seaports of New York, Philadelphia and Boston. Those from Asia arrived primarily at the port of San Francisco. Some Asians came for the California Gold Rush that began in 1849. Others, primarily Chinese contract laborers, came to build the western portion of the transcontinental railroad, which was completed in 1869.
