Marshall went on to become a federal appeals court judge, the nation's first black solicitor general and the first black justice on the U.S. Supreme Court. But long before Brown vs. Board of Education, Marshall was in the courthouse pushing for change.
"The first three big steps on the road to Brown occurred in Maryland, and Thurgood Marshall was involved in all of them," said Larry S. Gibson, who teaches a course called Racial Discrimination and the Law at the University of Maryland law school.
The first case involved Maryland's law school, which had years before barred an eager Marshall from attending because he was black.
In 1935, along with his mentor, friend and fellow NAACP lawyer Charles Hamilton Houston, Marshall won his first major civil rights case - Murray vs. Pearson - successfully integrating the law school that had once kept him out.
In 1936, brimming with the joy of victory, Marshall jumped right in to another Maryland discrimination case, Williams vs. Zimmerman - the second step on the road to Brown.
Margaret Williams, a teen-ager from Cowdensville, an all-black enclave in Baltimore County, had been denied access to Catonsville High School. The denial was routine: Baltimore County refused public education to black students past the sixth grade.
If Margaret, and any other student who wanted schooling past sixth grade, had passed an elementary school exit exam for blacks only, the county would have paid their way to attend high school in the city.
But Margaret twice failed the exam, ending her education at the seventh grade.
Representing Margaret Williams' family, Marshall argued that the county was obligated to either create a black high school in the county or allow black students to attend Catonsville High.
Marshall lost the case, and the subsequent appeal. But the fight would produce a surprising chit that Marshall would cash in later to successfully argue the Brown case.
"In the appeal, according to the NAACP, there was a line where the court pointed out that separate was never going to be really equal," Gibson said. "That gave kind of an indication of where the [future] cases and strategies should go. The case showed Marshall and Houston that the way to go was to thoroughly document the impact and the consequences of separation - which, of course, became an important part of the Brown decision some 18 years later."
The Williams case also produced another unexpected victory.
"Because of what he did," said Louis S. Diggs, a Baltimore County historian, "in 1937, when the appeal to the state went through, Baltimore County must have seen the handwriting on the wall." Two years later, the county system arranged for the high school curriculum to be taught at three black elementary schools to black students - in effect, creating high schools for county black students.
But discrimination didn't end there.
"That was just a stopgap measure," said John McGrain, also a Baltimore County historian. "They stuck with segregation even after that."
By that time, Margaret Williams' family had paid for her to go to a private school, her nephew Barry Williams, Baltimore County's director of employment and training, said. Margaret Williams, now 83, became a nurse and lives in Baltimore County.