In the 1600s and 1700s Spanish settlers migrated north from Mexico into Texas, New Mexico, and California. They set up missions, towns, and forts such as San Antonio, El Paso, Albuquerque, Santa Fe, San Diego, Los Angeles and San Francisco.
The cliff dwellings were built by the Anasazi, the ancestors of the Pueblo Indians. The Anasazi gre crops on the mesa above these cliffs and in river alleys below. The cliff dwellings were abandoned about 700 years ago, possibly after severe droughts.
In the 1900s the United States experienced major social, economic, and technological changes. The country fought in World War I in 1917 and 1918 and suffered through the Great Depression in the 1930s. U.S forces also fought in World War II from 1941 to 1945. Since then, the United States has been one of the richest and most powerful countries in the world.
Economic differences between the North and South, and the South's insistence on maintaning slavery, eventually led to Civil War. This war lasted for 5 years and ended with the defeat of the southern, or Confederate, states. The federal government then moved to end slavery throughout the country.
By 1830 the northeastern United States was industrializing. Industries and railroads spread. In the South, however, the economy was based on export crops like tobacco and cotton. Farmers grew these crops on plantations- large farms that produce one major crop. Many southern plantations used the labor of enslaved Africans.
After independence, the United States set up a federal system of government. Under the U.S. federal system power is divided between local, state, and national governments. Underlying all levels of government is the idea that ultimate power rets with the people. During the 1800s many Americans and immigrants migrated westward in search of more and better farmland.
The British became the major influence on the early history of United States. Beginning in the early 1600s they set up 13 colonies along North America's east coast. Other early settlers included Dutch and Germans. In 1619 Europeans began bringing enslaved Africans to the colonies.