Witness Post: Warner T. McGuinn
Reading a lead article in the Yale Magazine from December, 2025, I came across a fascinating story about Mark Twain (Samuel Clemens) and the famous Supreme Court judge, Thurgood Marshall. Tying these two together was a Black man named Warner McGuinn. Having never heard of McGuinn before, it was time for some help from ChatGPT. Below are some questions I posed to the Open AI’s LLM model, and summaries of the research the model unearthed as it dove into this fascinating character. As a bonus, Marshall is a famous native Baltimorean, and McGuinn met him in Baltimore.
Q: Who is Warner T. McGuinn and what are his connections with Mark Twain and Thurgood Marshall?
Warner Thornton McGuinn (1859–1937) was a pioneering African American attorney whose life created a direct link between the literary world of Mark Twain, a writer for the Hartford Current, and the legal landmark of Justice Thurgood Marshall.
Born in Richmond, Virginia, McGuinn graduated from Lincoln University (Chestertown, PA) in 1884 and initially studied law at Howard University (Washington, DC) before transferring to Yale Law School in 1885.
The Connection with Mark Twain
While at Yale, Warner McGuinn supported himself by working as a waiter, bill collector and bookkeeper. He served as a member of the Kent Club, a law school debating society, and was tasked with introducing Mark Twain to the Club, when the author was invited to speak on campus. The club president asked McGuinn to meet Mark Twain (Samuel Clemens) at the New Haven train station and escort him to the lecture at the Dean’s residence. On their walk to the Yale Campus, McGuinn impressed Clemens as someone who would make an excellent lawyer.
After their time together, Clemens was so captivated by McGuinn’s character and intellect that he wrote to the Dean of Yale Law, Francis Wayland, offering to pay for McGuinn’s law school expenses. Clemens wanted the student to be able to focus entirely on his studies. In a 1885 letter, Twain famously wrote:
“I do not believe I would very cheerfully help a white student who would ask a benevolence of a stranger, but I do not feel so about the other color. We have ground the manhood out of them, & the shame is ours, not theirs, & we should pay for it.”
With the writer Twain ‘s financial support, McGuinn flourished at Yale. In 1886 McGuinn won an oratory prize: he was chosen by a jury to receive the $100 Townsend Prize. The New Haven Journal-Courier declared McGuinn’s speech “a masterly piece of work and well delivered, as was the opinion of the judges and audience.” He graduated at the top of his Yale Law School class in 1887.
McGuinn started his practice in Kansas City, Kansas and eventually moved to Baltimore, Maryland, in 1891 where he founded his own law firm and became a distinguished civil rights lawyer. He was elected twice as a councilman to the Baltimore City Council from 1919 to 1923 and from 1927 to 1931. Each time he was fighting Democrats who tried to bar Black people from city patronage jobs.
McGuinn’s own notes document his law career and his outspoken support for civil rights. He argued against state and local Jim Crow laws that were being proposed in the early twentieth century, including segregation measures and a voting bill that had a “grandfather clause” designed to exclude Black people. He is credited with helping to get a residential segregation law overturned in Baltimore in 1917. He also spoke out publicly in favor of women’s suffrage.
McGuinn’s Career and Mentorship of Thurgood Marshall
Thurgood Marshall attended Frederick Douglass High School in Baltimore, then graduated with honors from Lincoln University in Pennsylvania (Class of 1930). That same year he was denied admission to the segregated University of Maryland Law School. Instead he attended Howard University Law School in Washington. He graduated at the top of his class (valedictorian) and earning his law degree in 1933.
Upon graduation from graduate school, the young Thurgood Marshall sought a job at Warner McGuinn’s firm; however, McGuinn refused to hire him, famously telling Marshall:
“You’re going to practice by yourself and get your brains kicked out and then come back to me and we’ll talk.”
McGuinn believed Marshall would learn the most about the practice of law in this country by starting his own firm. At the same time McGuinn supported Marshall by providing him with office space, sharing secretarial support, and passing him challenging legal cases. Marshall later described McGuinn as “one of the greatest lawyers who ever lived” and remarked that if McGuinn had been a White man, he surely would have been a judge.
Q: Is there more information on the specific civil rights cases McGuinn and Marshall worked on together in Baltimore?
While Warner McGuinn did not officially hire Thurgood Marshall as a law partner in 1933, the two shared a profound professional partnership in Baltimore, where McGuinn mentored Marshall through the early, career-defining cases of his legal practice. Without a doubt, those first few years together encouraged Marshall to learn about the consequences of unjust application of the Constitution and the practice in law. Despite the “founding father” platitudes, the law was not equal for all races or genders. McGuinn provided essential practical support that kept Marshall’s fledgling legal practice afloat.
Below are the key ways McGuinn and Marshall collaborated and the specific legal work they pursued together:
Office Collaboration and Mentorship
- Shared Infrastructure: McGuinn allowed Marshall to set up an office in the same building (the Phoenix Building at 4 Redwood Avenue in downtown Baltimore) and share his personal secretary and personal law library.
- Case Referrals: McGuinn frequently passed “difficult” or “losing” cases to Marshall to sharpen his skills and ensure he had a steady stream of work during the Great Depression.
- Tactical Advice: Marshall later credited McGuinn for teaching him how to navigate the specific “personalities and peculiarities” of the Baltimore court system, including the judges and prosecutors Marshall would face.
Key Cases and Legal Actions
While McGuinn often worked in the background, their collaboration was central to the following efforts:
- Voter Suppression Defense: Both men were relentless in fighting Maryland’s attempts to disenfranchise Black voters. McGuinn shared his extensive “scrapbooks” of evidence—clippings of politicians’ past racist stances—which Marshall used to build ammunition for his own voting rights litigation.
- Green v. Samuelson (1935): In this notable Baltimore case, McGuinn (alongside W.A.C. Hughes) defended Black activists who were picketing white store owners on Pennsylvania Avenue. This case, which centered on the right of Black residents to demand employment in stores where they spent their money, was a cornerstone of the legal environment in which Marshall was being trained.
- School Segregation Investigations: In 1936, McGuinn’s brother, Robert McGuinn, collaborated directly with Thurgood Marshall on his first major investigation into the poor conditions of segregated schools in Maryland. This research eventually fueled the NAACP’s long-term strategy to dismantle the “separate but equal” doctrine.
- Public Speaking and Activism: McGuinn and Marshall frequently appeared together at local NAACP meetings and civil rights rallies. McGuinn, known as a master orator since his days at Yale Law School, helped Marshall refine the storytelling techniques he would later use to win Brown v. Board of Education.
“He was the only one who helped me,” Marshall later recalled of Warner McGuinn, adding that without McGuinn’s early guidance, he might not have survived as a Black attorney during and beyond the 1930s.
Q: What is a list of the specific strategies McGuinn used to help Thurgood Marshall prepare for his first major victory against the University of Maryland?
In the landmark 1935 case Murray v. Pearson, Warner McGuinn played a critical role as Thurgood Marshall’s primary mentor and strategic advisor, helping him craft the legal blueprint that eventually integrated the University of Maryland School of Law.
While Charles Hamilton Houston co-counseled the legal case in court, Warner McGuinn’s decades of experience in the Baltimore City legal system provided the specific “ground-game” tactics used to outmaneuver the university.
The “In-State Equity” Strategy
The University of Maryland’s legal defense was that they fulfilled their “separate but equal” obligation by offering scholarships for Black students to attend out-of-state law schools. McGuinn and Marshall countered this argument with a highly effective, practical outcome of the scholarships:
- The Jurisdictional Gap: They argued that a Maryland lawyer must be trained in Maryland-specific law, which an out-of-state school (like Howard, Yale or Harvard) could not provide.
- Equal Opportunity, Not Equal Cash: They contended that a check for tuition was not an “equal facility” if it required a citizen to leave their home state to receive an education that white citizens could get locally.
The “Scrapbook” Strategy: Exploiting Precedent
McGuinn was famous for his scrapbooks, in which he meticulously recorded and archived the public statements and past rulings by many Maryland judges.
- Targeting the Judges: McGuinn advised Marshall on which judges would be most receptive to a strictly literal interpretation of the 14th Amendment.
- The “Trap” for Plessy: Instead of trying to overturn the famous ruling of Plessy v. Ferguson (which established “separate but equal”), they used it as a trap. They argued that since Maryland had no separate law school for Black students, they were failing the “separate but equal” test by their own standards and therefore must admit their Black plaintiff, Donald Gaines Murray, to the White-only school.
Trial Tactics and Preparation
Because Marshall was a young lawyer with little trial experience, McGuinn provided the essential professional scaffolding:
- Courtroom Personalities: McGuinn, having spent years studying the lawyers in Baltimore City, coached Marshall on the peculiarities of the Baltimore judiciary, helping him anticipate the aggressive questioning from the Assistant Attorney General.
- Key Outcome: The Maryland Court of Appeals ruled in their favor in 1936, forcing the integration of the law school in Baltimore, thereby making it the first major school desegregation victory in U.S. history and a precursor to the landmark Brown v. Board of Education.
Q: Is there more we should know about the specific “scrapbook” evidence McGuinn used to track the records of judges and politicians?
Warner McGuinn’s “scrapbook” strategy was a meticulous method of data collection that predated modern legal databases, providing Thurgood Marshall with a powerful weapon for civil rights litigation.
According to the records, here is how the strategy worked and what it contained:
The “Scrapbook” Strategy: Exploiting Precedent
- Voter Suppression Ammunition: McGuinn shared extensive clippings of politicians’ past racist stances, which Marshall used to build evidence for his own voting rights cases.
- Strategic Legal Argument Prep: These archives allowed Marshall to anticipate the peculiarities of the Baltimore judiciary and prepare for aggressive questioning from state officials.
By documenting the contradictions in the legal system, McGuinn’s scrapbooks helped turn the state’s own laws and public statements against the segregated establishment.
Warner McGuinn died in 1937 in Philadelphia; he was survived by a daughter, Alma and a grandson. McGuinn’s wife of 37 years, Anna Wallace, had died in 1929.
[] Yale Magazine
Henry E. Hooper 