While the roots of the detective novel go back to the 19th century, the genre reached its height around 1925 to 1945. This work presents information on 21 British and American women who wrote during the 20th century. As a group they were largely responsible for the great popularity of the detective novel in the first half of the century. The British authors are Dora Turnbull (Patricia Wentworth), Agatha Christie, Dorothy L. Sayers, Elizabeth Mackintosh (Josephine Tey), Ngaio Marsh, Gladys Mitchell, Margery Allingham, Edith Pargeter (Ellis Peters), Phyllis Dorothy James White (P.D. James), Gwendoline Butler (Jennie Melville), and Ruth Rendell, and the Americans are Patricia Highsmith, Carolyn G. Heilbrun (Amanda Cross), Edna Buchanan, Kate Gallison, Sue Grafton, Sara Paretsky, Nevada Barr, Patricia Cornwell, Carol Higgins Clark, and Megan Mallory Rust. A flavor of each author's work is provided.