each book, Perkins would try to interview an individual who grew up in the given country to gain an understanding of the particular customs. Later books in the series, such as The American Twins of the Revolution, supplanted history for geography as the basis of the twins' backgrounds. Perkins sold more than 2 million copies of her books and was Houghton Mifflin's most profitable author. Her final book, The Dutch Twins and Little Brother, was published posthumously in 1938. She died in Pasadena, California, of a heart attack from coronary thrombosis on March 18, 1937; she had recently moved there with her husband in an effort to restore her health. Perkins had two children: Eleanor Ellis, a writer, and Lawrence Bradford, an architect. Perkins' book The Dutch Twins is known to have inspired popular children's author Beverly Cleary to start reading. Perkins also provided illustrations for Edith Ogden Harrison's series of fairy tales, published in the early years of the 20th century. A public school in the Big Oaks neighborhood of Chicago was named after Perkins. The school was built for K-6 students. When it opened, there was an oil painting of Perkins displayed in the hallway near the main entrance. The school and property were later sold and the block was developed with single family homes. Selected works Prince Silverwings and Other Fairy Tales, written by Edith Ogden Harrison (McClurg, 1902) – first of several collaborations with Harrison The Goose Girl: A mother's lap book of rhymes and pictures (McClurg, 1906) Before beginning the Twins series Perkins illustrated, and sometimes contributed as editor or writer, to new editions of Aesop's fables, Anderson and Grimm fairy tales, Hawthorne's classical mythology, and Robin Hood. Twins series (complete) Geographical series The Dutch Twins (1911) The Japanese Twins (1912) The Irish Twins (1913) The Eskimo Twins (1914) The Mexican Twins (1916) The Belgian Twins (1917) The French Twins (1918) The Scotch Twins (1919) The Italian Twins (1920) The Puritan Twins (1921) The Swiss Twins (1922) The Filipino Twins (1923) The Farm Twins (1928) The Pickaninny Twins (1931) The Chinese Twins (1934) The Norwegian Twins (1933) The Spanish Twins (1934) The Dutch Twins and Little Brother (1938) The Dutch Twins Primer Historical series The Cave Twins (1915) The Spartan Twins (1918) The Colonial Twins of Virginia (1924) The American Twins of 1812 (1925) The American Twins of The Revolution (1926) The Pioneer Twins (1927)