During the 1970s and '80s, this painter made several portraits  of Helga Testorf.
An African American is seated in front of clothes hanging on hooks in this artist's A Crow Flew By.   One work by this artist shows red, white, and blue streamers on the handlebars of a bicycle and a  matching feather on top of a pole on the same bike, which is ridden by a boy looking away from the   picture. That work is Young America. During the 1970s and '80s, this painter made several portraits  of Helga Testorf. One of his works shows tire tracks on the right side leading to a farmhouse, toward  which a polio-stricken woman pulls herself. Name this artist who lived in Pennsylvania and Maine  and who painted Christina's World.
An African American is seated in front of clothes hanging on hooks in
Andrew (Newell) {Wyeth}