What is Douglas Stuart Moore's best remembered for?

Context: Douglas Stuart Moore was an American composer, songwriter, organist, pianist, conductor, educator, actor, and author. A composer who mainly wrote works with an American subject, his music is generally characterized by lyricism in a popular or conservative style which generally eschewed the more experimental progressive trends of musical modernism. Composer Virgil Thomson described Moore as a neoromantic composer who was influenced by American folk music. While several of his works enjoyed popularity during his lifetime, only his folk opera The Ballad of Baby Doe has remained well known into the 21st century.

Answer: The Ballad of Baby Doe (1956) as it has remained well known into the 21st century.