Earl Warren was a California district attorney of Alameda County, the 20th Attorney General of California, the 30th Governor of California, and the 14th Chief Justice of the United States . As Chief Justice, his term of office was marked by numerous rulings affecting, among other things, the legal status of racial segregation, civil rights, separation of church and state, and police arrest procedure in the United States. In the years that followed, the Warren Court became recognized as a high point in the use of the judicial power in the effort to effect social progress in the U.S. and Warren himself became widely regarded as one of the most influential Supreme Court justices in the history of the United States and perhaps the single most important in the 20th century .