The United States federal government has no formally established official language, but it does use English for legislation, regulations, executive orders, treaties, federal court rulings, and all other official pronouncements. In some states, English, French, Spanish or Hawaiian are official. In 2000, the census bureau printed the standard census questionnaires in six languages: English, Spanish, Korean, Chinese, Vietnamese, and Tagalog. The English-Only movement seeks to establish English as the only official language of the nation.
English was inherited from British colonization and it is spoken by the vast majority of the population, although more than 80 percent of Americans have no British ancestors. It serves as the de facto official language, for instance as that in which government business is carried out. According to the 1990 census, 97 percent of U.S. residents speak English ‘well’ or ‘very well.’ Only 0.8 percent speak no English at all, as compared with 3.6 percent in 1890. American English has some differences from British English. For detailed differences in British English and American English see American and British English differences.
The second-most common language in the country is Spanish, spoken by about 28.1 million people (or 10.7% of the population) in 2000. The United States is the fifth country in the world in Spanish-speaking population, outnumbered only by Mexico, Spain, Argentina, and Colombia. Although many new arrivals have various levels of English-proficiency, Hispanics who are second-generation American in the United States almost all speak English, but only about 50 percent still speak Spanish. The territory of Puerto Rico is predominately Spanish-speaking. Many Puerto Ricans migrate to New York City, New York, adding to the Spanish-speaking population there. For a detailed history of Spanish in USA from 15th century on, see Spanish in the United States. Spanglish is a pidgin of Spanish and English and is spoken in areas with large semi-bilingual populations of Spanish and English speakers, such as along the U.S. - Mexico border, Florida, and New York City.
The USA has long been the destination of many immigrants. From the mid 19th century on, the nation had large numbers of residents who spoke little or no English, and throughout the country there have been towns and neighborhoods of cities where business, schools, and newspapers were in languages such as German, Italian, Czech, Polish, Chinese, Yiddish, etc. Currently, Asian languages account for the majority of languages spoken in immigrant communities: Korean, various Chinese languages, Vietnamese, and Tagalog. Historically, the original languages of immigrants tend to disappear or become greatly reduced through assimilation and generational change.
Before World War I, more than 6 percent of American schoolchildren received their primary education exclusively in German. Currently, although more than 45 million Americans claim German ancestors, only 1.5 million speak the language. The Amish speak a dialect of German known as Pennsylvania Dutch. There is a myth that German was to be the official language of the US, in order to more clearly sever ties with Great Britain, but this is inaccurate. It is based on a failed early attempt to have government documents translated into German. 
Creole and Cajun, a variant of French, are spoken in some parts of Louisiana (part of a former French colony). There are French Canadian settlers in parts of northern New England, as well. More than 13 million Americans claim French ancestry, but only 1.5 million speak that language.
The various Native American languages, of course, predated the European settlement of the New World, and in a few parts of the USA continue to be spoken. Most of these languages, however, are moribund, despite efforts by native peoples to revive them. Exceptions to this include Navajo, with over 100,000 native speakers, Lakota, Hopi and several others. Native languages played an important role in World War I and World War II, when they were spoken by native peoples as codes. In some cases, the languages were spoken outright over the radio, while in other cases, such as Navajo, codes were developed, using the language as a basis. With fewer than thirty people outside the United States able to speak the language, the code remained unbroken.
Some African-American activists insist that Ebonics, also known as African-American Vernacular English, the dialect of English spoken in many African-American sections of American urban areas, is not simply a dialect, but an entirely different language, and are urging that their language be accepted as an equal to American English.
American Sign Language (ASL) is the language used by many deaf people in America. Unlike Signed English, ASL is a natural language in its own right, not a symbolic representation of English. The US Census Bureau did not gather data on ASL when compiling the list of "primary language at home" shown above, but estimates of the number of ASL users would place its ranking anywhere from 3rd to 10th in the list. There are at least two other important sign languages used in the United States: Martha's Vineyard Sign Language and Hawaii Pidgin Sign Language.