• Baldwin Library of Children’s Literature Digital Collection  The Baldwin Library of Historical Children's Literature at the University of Florida's George A. Smathers Libraries contains both English and American books from the early 1700s through the current year.  The digital collection numbers 2,500 books and also includes the popular American magazine, St. Nicholas Magazine (1873-1941), which first serialized many children’s classics. 
• Merrycoz.  About 19^th Century American children and what they read.  Primarily an index to periodicals c.1800-1872: Youth's Companion;  Juvenile Gazette (Providence, RI); Parley's Magazine; Youth's Magazine (Cincinnati, OH); The Slave's Friend; Robert Merry's Museum; Woodworth's Youth's Cabinet; The Student; The Schoolmate; Student and Schoolmate; Our Young Folks; The Little Corporal  Site also contains a small collection of HTML text (and some images) from about 2 dozen books
• Children's Literature: Digitized print material from the Rare Book Room, Library of Congress.  19th and early 20th c. with "page turner" PDF presentation
• 19th Century Schoolbooks; 140 textbooks from the Prof. John Neitz collection at the University of Pittsburgh.
• 19th Century Girls' Series.  Biography, bibliography and selected e-texts (mostly HTML) from popular series.
• Alice's Adventures Under Ground. Lewis Carroll's original manuscript (c. 1864), using a British Library virtual viewer.
• Boy's Own Paper. 1912-3. This paper was a weekly British story paper geared towards young boys. It contained stories, educational pieces, and advice columns.
• The Tar Baby and the Tomahawk (Univ. of Nebraska, Lincoln and Washinton Univ. St. Louis) Site offers 100+ original children's texts from 1880-1939, many of which were popular in their day but are now considered out-dated or problematic for their views and representations of race. Also offers contextualizing essays on themes and issues of the literature.
• Brownies' Book, The was a literary magazine for African American children and their parents, published by W.E.B. DuBois from 1920-1921, including stories, photos, poetry, and biographies of prominent African Americans.
• Celebration of Women Writers contains high quality images and often transcribed text of children's books, among others, from the mid 1800's through the mid 1900's.
• Children's Books Online: The Rosetta Project: nice collection of late 19th c. and early 20th c. books with rough genre categories, but otherwise not very accessible except for browsing. See for example The Pied Piper of Hamelin (1888) and Frances and Henry (1880).
• Children's Series Books Online. Note, not all are full digital editions; site indexes free sites in plain text and html editions, such as Project Gutenberg. Series include Horatio Alger, Bobbsey Twins, L. Frank Baum's Oz books, and many more.
• The Cinderella Project (Univ. of Southern Mississippi): text and image archive containing a dozen versions of the fairy tale.
• Digital Dime Novels (University of Minnesota Libraries) About 15 complete novels (pdf) from the late 1800s to early 20th c. Examples include "The Young Marooner" from Brave and Bold Weekly (1908) and "Log Cabin Library" (1889-97).
• Dime Novels and Penny Dreadfuls (Stanford University) more than 8,000 items, including long runs of the major series: Happy Days and Frank Leslie's Boy's of America. Site has guided tours, for example of print processes and 19th c. dime novel covers.
• Elizabeth Nesbitt Room Nineteenth Century Juvenile Magazine Collection (University of Pittsburgh) About 85 U.S. and British periodicals published between 1802 and 1943. Includes title index, publisher’s index and bibliography. Nice collection of covers, and sample pages and illustrations, but not full text.
• Girl's Own Paper 1880-89, 1886 issues. This piece of history was a weekly printed British story paper geared towards young girls. It contained stories, educational pieces, and advice columns.
• International Children’s Digital Library Digital Library of children’s books (about 2,500) from the 1500’s to present day in 41 different languages. From home page, go to “Read Books,” then click “Advanced Search” to search by publication date or a variety of other features.
• Internet Archive: Children’s Library These digital books have been collected from other public sites listed above, but the interface is attractive for browsing.
• Jack and the Beanstalk (Univ. of Southern Mississippi) text and image archive containing several English versions of the tale.
• Little Red Riding Hood Project (Univ. of Southern Mississippi) text and image archive containing sixteen English versions of the tale.
• Look Glass for the Mind: 350 Years of Books for Children. University of Washington Digital Collection.
• Oz Collection (Univ. of Minnesota) 15 Oz books digitized cover-to-cover.
• Shaping the Values of Youth: Sunday School Books in 19th c. America (Michigan State). More than 100 titles, covering such topics as immigrants, holidays, and temperance. 
• Sunday School Books: Shaping the Values of Youth in Nineteenth-Century America (Library of Congress American Memory) 163 books published in America between 1815 and 1865 documenting the religious instruction of Antebellum youth. Complete html text and related page images.
• SurLaLune Fairy Tales More than 1,600 folktales and fairytales in digital format from around the world.
• Young American Readers (Monaghan Collection of Books on the History of Reading in the United State, Univ. of Kansas) Nice exhibit with digitized examples in the history of early American reading instruction.

These books may help you in your analysis of a "lost" children's work.

• American Periodical Series (APS)  Digitized images of the pages of American periodicals from 1740 to 1900.  Easiest way to search: use "Publications Search" and use the "Narrow by Subject" option to list the 27 children's periodicals. All articles are presented in pdf format.
• Early American Imprint Series 1: Evans, 1639-1800.  Also known as the "Evans Bibliography".  Full text database of publications from colonial America and the early republic (1639-1800).  You may Browse by Genre and select “Juvenile Literature,” "Spellers", etc.  Note the ability to search by keyword within the genre.  Or, Browse by Subjects, select category: “Literature,” and select from sub-headings such as “Children’s Literature,” “Children’s Poetry,” “Children’s Stories,” “Fables,” or “Fairy Tales.”
• Eighteenth Century Collections Online (ECCO) has a wealth of books for children in full image; however the searcher must begin with known authors and titles, or keyword in titles, such as "spelling."  Try, for example, Aesop or John Bunyon's A Book for Boys and Girls.
• Everyday Life of Women in America, 1820-1900.  Includes both books and periodicals, most aimed at women and some at adolescents.  One periodical for youth is The Rose Bud, or Youth's Gazette, published in Charleston, 1832-34.  Nice digital images for browsing.

For additional sources consult MARQCAT using subjects such as: Children's literature--history and criticism; Children--books and reading--history; Children's literature, American--history and criticism; Children's literature, English--history and criticism

Children's Books in England & America in the Seventeenth Century. William Sloane (Columbia University, 1955) Memorial Level 5 Z1037 .S62

A Critical History of Children's Literature (Revised ed.).Cornelia Meigs, et al, eds.(Macmillan, 1969). Memorial Level 4 PN1009. A1M4 1969

English Children and Their Magazines, 1751-1945 (Yale University Press, 1988) Memorial Lvl 4 Lower PN 5124 .J8 D72 1988

The Osborne Collection of Early Children's Books 1566-1910: a Catalogue (Toronto Public Library, 1958) Memorial Level 5  Z1038.T6 A55