An ongoing compendium of secondary sources for comic strip history I have found valuable.

Books

1. Berger, Arthur Asa. The Comic-Stripped American; What Dick Tracy, Blondie, Daddy Warbucks, and Charlie Brown Tell Us About Ourselves. New York: Penguin, 1973
2. Blackbeard, Bill. R.F. Outcault’s The Yellow Kid: A Centennial Celebration of the Kid Who Started the Comics. Northampton, 1993.
3. Canemaker, John. Winsor McCay : His Life and Art. Revised, Expanded Edition, New York: Harry N. Abrams, 2005
4. Harvey, R.C.. The Art of the Funnies: An Aesthetic History
5. Harvey, R.C.. The Children of the Yellow Kid.
6. Harvey, R.C. Milton Caniff
7. Marshall, Richard. America’s Great Comic Strip Artists. New York: Abbeville Press, 1989.

Online Articles

1. R.C. Harvey. “Outcault, Goddard, The Comics and the Yellow Kid.” The Comics Journal, 2016. Web Site
2. Westbrook, David. “From Hogan’s Alley to Coconino County: Four Narratives of the Early Comic Strip.” 1999: Web Site