1n 1924, Sampson opened a law office on the South Side of Chicago, serving the local black community. From 1925 through 1942, she was associated with the Juvenile Court of Cook County and served as a probation officer. In 1927 Sampson became the first woman to earn a Master of Laws from Loyola University‘s Graduate Law School. She also passed the Illinois State Bar exam that year. In 1934 Sampson was admitted to practice before the Supreme Court. In 1943, she became one of the first black members of the National Association of Women Lawyers. In 1947 she was appointed an Assistant State’s Attorney in Cook County.
The article goes on to state that President Truman appointed Sampson as an alternate U.S. delegate to the United Nations in August 1950, making her the first African-American to officially represent the United States at the UN. She was a member of the UN’s Social, Humanitarian, and Cultural Committee, where
she lobbied for continued support of work in social welfare. She also presented a resolution
pressuring the Soviet Union to repatriate the remainder of its Prisoners of War from World War II. She was reappointed to the UN in 1952, and served until 1953. During the Eisenhower Administration, she was a member of the U.S. Commission for UNESCO. In 1961 and 1962, she became the first black U.S. representative to NATO.