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Traditional American values placed great emphasis on the importance of the family.For most Americans in the 18th and early 19th centuries，the family was a working unit as the majority of Americans lived on farms where every member of the extended family worked to help make a living.Couples married for economic reasons.Servants and apprentices sometimes lived in the same house as the family they worked for and were regarded as part of the family.

In the second half of the 19th century，the nuclear family consisting of a husband and wife and their dependent children became the typical model for most Americans.Marriage was no longer as often for economic reasons only.However，things began to change in the 1960s.In the 1950s and early 1960s，the enormous material wealth available to Americans caused women to believe in more equality and social justice as well.As a result，in the late 1960s and early 1970s，more women began to take jobs outside the home and to develop careers.This had enormous impact on the family.

As more women worked outside the home and demonstrated that they were men’s intellectual equals and could also support the family financially，they demanded the end of discrimination and sought more self⁃fulfillment.They became less tolerant of marriages that lacked love and affection.Partially as a result，divorce rates rose quickly in the 1970s and 1980s.Today，about half of all marriages end in divorce.The high rate of divorce and separation left many children living with only one parent.About a quarter of all children under the age of 18 currently live in single⁃parent families.Most single⁃parent families are headed by women.

The average size of American families is becoming smaller and smaller.The high cost of living and the stagnation of real wages for most workers since the 1970s make it necessary for a family to have two incomes to support a middle⁃class standard of living.So，many women work full⁃time jobs and cannot raise children at the same time.As a result，they choose to have fewer children.86％ of all American families today have two children or less，and many couples choose not to have children at all.

Another change to the traditional nuclear family comes from increased tolerance for homosexuality.Homosexual relationships were traditionally regarded as unhealthy，immoral and harmful to society.But during the 1960s and 1970s when society as a whole was becoming more concerned about the rights of individuals or disadvantaged groups.By 2015，37 states，the District of Columbia and 23 Native American tribal jurisdictions had legalized same sex marriage.Religious fundamentalists and the much of the Republican Party have been fighting against this trend as part of their efforts to restore traditional social mores.