Born in 1921 to immigrants from the island of Nevis, West Indies, Constance Baker Motley grew up in New Haven, Connecticut, among Irish, Italian, Jewish, and Russian immigrants. New Haven was relatively integrated, but in high school, Motley was denied admission to a local skating rink and public beach because of her race. She joined the local chapter of the National Association for the Advancement of Colored People (NAACP) and worked with other community organizations in the 1930s.

As an honors student in high school, Motley decided to pursue a legal career to combat discrimination. She later recalled: "No one thought this was a good idea, and I received no encouragement. My mother thought I should be a hairdresser; my father had no thoughts on the subject." In a speech given at a local community center, Motley impressed a wealthy Connecticut businessman, Clarence Blakeslee, who offered to pay her way through college. After Motley graduated from New York University, she attended Columbia Law School and worked as a law clerk for NAACP attorney Thurgood Marshall.

When she graduated from law school in 1946, Motley became a legal assistant for the National Association for the Advancement of Colored People's Legal Defense and Educational Fund (LDF). There, she worked on school desegregation cases, conducting research and preparing briefs leading up to the landmark Supreme Court case Brown v. Board of Education (1954). She eventually earned associate counsel status and became the LDF's principal trial attorney during the most contentious and racially volatile years of the Civil Rights movement. In Meredith v. Fair (1962), Motley successfully argued to the United States Court of Appeals for the Fifth Circuit that James H. Meredith should be admitted to the University of Mississippi.

In addition to advocating racial equality in schools, Motley also used the courts to fight against discrimination in housing, public accommodations, transportation, and voting rights. From 1964-65, she served in the New York state senate as its first African American female senator. In 1965, she became the first African American woman elected to the presidency of New York City's Manhattan borough.

In 1966, Motley was appointed by President Lyndon B. Johnson to the U.S. District Court for the Southern District of New York, the nation's largest federal bench. This appointment made her the first African American woman to be appointed to a federal judgeship. In 1982, Judge Motley was made chief judge, and in 1986, she acquired senior status.