In 1938 he was awarded the Pulitzer Prize for Reporting for a series of articles in the Post-Gazette[2] proving that Hugo Black, newly appointed as a justice to the United States Supreme Court by President Franklin Roosevelt, had been a member of the Ku Klux Klan in Alabama.
Passing as a black man, he was supported by the NAACP and accompanied by John Wesley Dobbs, a prominent 66-year-old political leader and early civil rights activist from Atlanta.
When Sprigle returned to Pittsburgh he wrote 21 powerful and passionate first-person articles that exposed white readers to the oppression, discrimination and humiliation that 10 million black Americans were being subjected to every day by the South's system of legal segregation.
The series, featured on the front page of the Pittsburgh Post-Gazette under the title I Was a Negro in the South for 30 Days, reported on a range of social, political and economic issues, including the inferiority of segregated black public schools.
[6] Sprigle's undercover journalism preceded by more than a decade novelist John Howard Griffin's similar but much more famous effort to learn what daily life was like for a Southern black man.