District Judge William D. Quarles, Jr. graduated from the University of Maryland in 1976. He received his law degree from the Catholic University of America in Washington, D.C. in l979.

After law school, Judge Quarles served as law clerk to the Honorable Joseph C. Howard, U. S. District Judge for the District of Maryland, from 1979 to 1981.

In 1982, Judge Quarles joined the United States Attorney's Office for the District of Maryland. He served as Coordinator of the President's Regional Organized Crime and Drug Enforcement Task Force.

In 1986, Judge Quarles joined the law firm Venable, Baetjer and Howard and was elected Equity Partner in 1987. He served as head of the firm's D.C. office Litigation practice group.

In 1996, Judge Quarles was appointed to the Circuit Court for Baltimore City. On September 12, 2002, he was nominated for United States District Judge by President George W. Bush. Judge Quarles was confirmed by the United States Senate on March 12 and commissioned on March 24, 2003.  Judge Quarles retired from the U.S. District Court for the District of Maryland on February 1, 2016.

Judge Quarles was also the author of Summary Adjudication: Dispositive Motions and Summary Trials, with others (John Wiley & Sons 1991).

Judge Quarles was admitted to the Bar of the District of Columbia in 1979; he was admitted in Maryland in 1991. He served on the Executive Council of Parents of Loyola College and on the Board of the Library Corporation of Loyola and Notre Dame Colleges. He also served as a lector in his parish. In 2005, Judge Quarles was given the Distinguished Alumni Award by the Black Law Student Association of the Catholic University of America School of Law.