Richard H. "Dirk" Gringhuis (22 September 1918 – March 1974) was the artist who illustrated the 39th Oz book, The Hidden Valley of Oz (1951). He was born in Grand Rapids, Michigan, and trained at the American Academy of Art in Chicago. He wrote and illustrated 28 books, half of them on Michigan history. He served as Curator of Exhibits at the Museum and Associate Professor in Elementary Education at Michigan State University. He also had experience as a television producer and on-air host, with the program "Open Door to Michigan."