Marshall received his law degree from Howard University in 1933, and set up a private practice in Baltimore. The following year, he began working with the Baltimore NAACP. He won his first major civil rights case, Murray v. Pearson, in 1936; his co-counsel on that case was Charles Houston.
Marshall won his first Supreme Court case, Chambers v. Florida 309 US 227 1940. That same year, at the age of 32, he was appointed Chief counsel for the NAACP. He argued many other cases before the Supreme Court, most of them successfully, including Smith v. Allwright 321 US 649 1944, Shelley v. Kraemer 334 US 1 1948, Sweatt v. Painter 339 US 629 1950, and McLaurin v. Oklahoma State Board of Regents 339 US 637 1950. His most famous case as a lawyer was Brown v. Board of Education of Topeka 347 US 483 1954, the case in which the Supreme Court ruled that "separate but equal" public education was illegal because it could never be truly equal.
President Kennedy appointed Marshall to the Second Circuit Court of Appeals in 1961. A group of white southern Senators held up his confirmation, so he served for the first several months under a "recess appointment." Marshall remained on that court until 1965, when President Lyndon Johnson appointed him Solicitor General. Johnson then appointed him to the Supreme Court in 1967, saying that this was "the right thing to do, the right time to do it, the right man and the right place."
Marshall served on the Court for the next twenty-four years, handing down opinions in several key cases.