He served in the United States Army Air Forces during World War II as a test pilot, flying P-38s and P-59 jets in extreme cold-weather.

[1][2] Markey returned to Chicago following the war, specializing his private legal practice in patent law and other areas of intellectual property.

He was reassigned by operation of law on October 1, 1982, to the United States Court of Appeals for the Federal Circuit, to a new seat authorized by 96 Stat.

[1] In 1997, the United States Congress renamed the Federal Circuit's Washington, D.C. headquarters the Howard T. Markey National Courts Building.

Congressman Henry Hyde (R-IL), then-Chairman of the House Judiciary Committee, said that Markey's efforts had established the Federal Circuit as "the world's most respected and followed court on matters of intellectual property.