The mid-20th-century arrival of the baby boomers provided a growing market for children's music as a separate genre. Woody Guthrie, Pete Seeger and Ella Jenkins were among a cadre of politically progressive and socially conscious performers who aimed albums to this group. During this time, such novelty recordings as "Rudolph the Red-Nosed Reindeer" (a Montgomery Ward jingle that became a book and later a classic children's movie) and the fictional music group, The Chipmunks, were among the most commercially successful music ventures of the time ("The Chipmunk Song" was a No. 1 hit single in 1958). TV personality Bob Keeshan ("Captain Kangaroo") recorded several children's albums, as did Shari Lewis.