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 twenty British and American women who wrote during the 20th century. As a group they were responsible for the great popularity of the detective novel in the first half of the century. The British authors are Sora Turnbull (Patricia Wentworth), Agatha Christie, Dorothy Sayers, Elizabeth Mackintosh (Josephine Tey), Gladys Mitchell, Margery Allingham, Edith Pargeter (Ellis Peters), Phyllis Dorothy James White (P.D. James), Gwendolyn Butler (Jennie Melville), and Ruth Rendell, and the Americans are Patricia Highsmith, Carolyn Heilbrun (Amanda Cross), Edna Buchanan, Kare Gallison, Sue Grafton, Sara Paretsky, Nevada Barr, Patricia Cornwell, Carol Higgins Clark, and Megan Rust. A flavor of each author's work is provided.