Born Julian Kitchen Lamar Miller in Augusta, Georgia, he shortened his name to Lamar in 1922 to honor his mother’s family and to make his name more memorable as an artist. Although he began painting as a child, his family encouraged him to attend the United States Military Academy, from which he graduated in 1918. After the Armistice, he resigned his commission to concentrate on his career as an artist. Lamar lived for a while in Chicago, then moved to New York in 1920.
He maintained an active studio in New York, but traveled extensively to paint his subjects in their native surroundings. He painted many prominent figures, including Prime Minister Winston Churchill; President Franklin D. Roosevelt; Franklin H. Martin, President, American College of Surgeons; and Governor Frank Dixon, Alabama. He was also an accomplished landscape painter.