Loper was born on the East Side of Wilmington, Delaware, and became interested in art when he was 20 years old. He began working for the Index of American Design of the Works Project Administration (he worked there for 5 years). In 1947, he began offering instructional classes from his studio, and during his career, he taught hundreds of students, including at the Delaware Art Museum, Lincoln University (MO), and the Jewish Community Center. While mostly self-taught, he did study at the Barnes Foundation off and on for 10 years. He stressed to his own students to paint what they see and not how someone else might see it. In the 1950s, his style fractured the plane of the composition, and his work became more colorful. His work is included in the collections of the Delaware Art Museum, Philadelphia Art Museum, the Corcoran Gallery (Wash., D.C.), Howard University, Clark Atlanta University, and the Pennsylvania Academy of Fine Art, among others. The Delaware Museum presented a retrospective of his work in 1996.