The sites covered are Feeding America, HEARTH—Home Economics Archive Research Tradition History, Google Books, University of Barcelona, Culinary & Dietetic Texts by Thomas Gloning, Medieval & Renaissance Food & Brewing Homepages by Greg Lindahl,and thousandeggs.com
With hundreds of cookbooks and many more related books, Google has become the largest collection of freely accessible e-texts, on any subject, on the web from the 18th century to the present.
Philadelphia authors range from Eliza Leslie's four cookbooks and many of her other works, to twelve of Sarah Tyson Rorer's cookbooks, including one published by Burpee's: "How to Cook Vegetables," 1891.
Gardening books by the famed Richard Bradley (four titles) and Phillip Miller's "Gardener's Directory" and "Gardener's Kalendar" as well as American authors such as Thomas Green with the 1828 and 1842 editions of his "New American Gardener" are varied and numerous.
The most efficient way to search is to go to Advanced book search. Type in keywords, author, or title and select dates to narrow the results (ie. 1800-1830). Some books, generally the recently published, offer only a 'limited preview.' The powerful search engine finds subjects among the works, and each book can be searched individually.
Feeding America: The Historic American Cookbook Project
Michigan State Library has put 76 of their historical cookbooks from 1798 to 1922 on the internet. The web site also contains a glossary, museum objects, articles and a video tour of the collection and how to read old recipes.
To view a particular book, simply click on “The Authors” and then on the author’s name. The biography and sources essay is worth reading on this page. Click on the title and that page has information and a synopsis of the book. Although you may be tempted to “View Page Images,” peruse the text by clicking on “Read Transcript.” At this point you can cut and save particular recipes. When you do find a page you want to view as the scan, click on the blue hyperlink “View Page.” If you want to copy the illustration, click right on your mouse and ‘save picture as’ then crop the image from page in Photoshop or other image editing software program.
If you don’t know which book you want, click on the “Browse the Collection.” The books are listed alphabetically, by publication date and by subject. This is simpler than using the “Book Author” or “Book Title” options on the “Search the Collection” page.
“Search the Collection” allows you to type in a recipe name or ingredient. A list with links appears. I have found that not all books which really do have the requested recipe are included in the list, even if you use all the variant spellings [ie. cup cake or cup-cake]. It is a good starting point, but you should know the books you read through often to add their recipe to the list if necessary.
When searching for Colonial period and earlier cookbooks on the net, four sites are particularly helpful. There are several other good ancient, medieval and renaissance web sites that also include historic cooking.
Culinary & Dietetic Texts by Thomas Gloning. 1350-1800
Gloning has put on the net an extensive German collection, European and the following authors in English: Bradley [1728-32], Murrell , The Good Huswifes Handmaide for the Kitchen  and A Proper Newe Booke of Cokerye [16th]. The site covers cookery, food, nutrition and dietetics with a good links list for ‘Coffee, Tea & Chocolate’, and one on ‘Old Wine Texts’.
Medieval & Renaissance Food & Brewing Homepages by Greg Lindahl.
Lindahl has a links list to a variety of period brewing and cook books. Of note is his ‘Medieval and Renaissance Clip-Art Collection’.
thousandeggs.com and culinaryhistory.org by Cindy Renfrow
This site has links to ancient and medieval cooking and brewing books in various languages, many in English and Dutch. She also has made a ‘Glossary of Medieval & Renaissance Culinary Terms’.
The Cornell University Library site has put online complete books and journals from 1825-1950. The cooking related books range from Child’s The Family Nurse, 1837, and Corson’s Cooking School Text Book, 1879, to Mitchell’s The Fireless Cook Book, 1913, and Goudiss’ Foods that will Win the War, 1918.
Click on “subjects” to see all the areas covered. Links lead to an informational essay and bibliography on subjects such as Food & Nutrition, Clothing & Textiles and Hygene [includes Care of the Sick].
The collection can be “browsed” by author, title or date. The “search” link allows searching the full text for a recipe name, ingredient or your subject of interest. The researcher can also type in a title or author.