Markos came to the United States following World War II and worked as a portrait painter in New York City, painting celebrities such as John Wayne, Robert F. Kennedy, President Ronald Reagan, and Pablo Casals.

[citation needed][1] In the 1960s, he moved to Houston, Texas, where he sparked an interest in Western American art.

JP Morgan acquired his works, which are housed today at its main headquarters.

Paintings of Sam Houston, Robert E. Lee, and George S. Patton are in private collections.

Robert F. Kennedy assisted Markos in obtaining permission to return to his home country, behind the Iron Curtain, in the early 1960s.