He served overseas with the American Expeditionary Forces during World War I, graduated from the Boston Museum School in 1921, and traveled to Europe on a postgraduate fellowship from his alma mater in 1922–23.

He returned to New York in 1932 to serve as curator of the American Wing of the Metropolitan Museum of Art, where he created exhibitions and authored more than 150 publications in venues such as Magazine Antiques.

[1][2] He installed the first folk art (Pennsylvania German) period rooms ("House of the Miller at Millbach") ever put in place at an American museum.

However, his untimely death in Philadelphia on September 8, 1954, meant the three sequel volumes were never written.

[1][2] In 1955, the Joseph Downs Collection of Manuscripts and Printed Ephemera at Winterthur was named in his honor.