The GeoGems on this site came from personal experience (randomly visited places, read somewhere, heard somewhere, random online searches discoveries) and the following books:
All Over the Map: An extraordinary Atlas of the United States – David Jouris (Ten Speed Press, 1994) [funny names]
Amazing America -- Jane & Michael Stern (David Obst Books, Random House, 1978)
Amazing US Geography – Andrea Sutcliffe (John Wiley & Sons, 2001)
America Bizarro -- Nelson Taylor (St. Martin’s Griffin, 2000)
America’s Most Charming Towns & Villages – Larry T. Brown (Open Road Publishing, Cold Spring Harbor, NY, 2004)
America’s Strangest Museums: A Traveler’s Guide to the Most Unusual and Eccentric Collections – Sandra Gurvis (Citadel Press, 1996)
An Eccentric Guide to the United States – James Dale Davidson (Berkley Publishing, 1977)
Best Small Towns – Norm Crampton (M. Evans and Company, NY, 2002)
Birthplaces USA – A. J. Mullay (Edinburgh, UK: Wherewithal Books, 1998)
Cities Ranked & Rated – Bert Sperling & Peter Sander (Wiley, Hoboken, 2004)
Don’t Know Much About the 50 States – Kenneth C. Davis (Harper Collins, 2001)
Eccentric America – Jan Friedman (Bradt Travel Guides/Globe Pequot Press, 2004)
Fifty Fabulous Places to Raise a Family -- Lee Rosenberg & Saralee H. Rosenberg (Career Press, 1993)
Food Festival, USA – Becky Mercouri (Laurel Glen, 2002)
From Fiddletown to Tuba City – Philip Thayer & Robert Gumpertz (Workman, 1982) [funny names]
Fun Along the Road: American Tourist Attractions – John Margolies (Little, Brown & Co., 2002)
Little Museums-- Lynne Arany & Archie Hobson (Henry Holt & Co., 1998)
Offbeat Museums -- Saul Rubin (Santa Monica Press, 1997)
Passing Gas and Other Towns Along the American Highway – Gary Gladstone (Ten Speed Press, 2003) [funny names]
Places Rated Almanac -- David Savageau & Geoffrey Loftus (Macmillan, 1997)
Retirement Places Rated – David Savageau (Wiley, Hoboken, 2004)
Road Trip USA , 6th ed. -- Jamie Jensen (Avalon Travel, Berkeley, 2012)
The 100 Best Art Towns in America – John Villani (TheCountryman Press, Woodstock, VT, 2005)
The Big Book of American Trivia – J. Stephen Lang (Tyndale House, 1997)
The Great Towns of America – David Vokac (West Press, San Diego, 1998)
The Largest U.S. Cities Named after a Food – Brandt Maxwell (Santa Monica Press, 2004)
The New Roadside America -- Mike Wilkins, Ken Smith & Doug Kirby (Simon & Schuster, 1992)
Unauthorized America: A Travel Guide to the Places the Chamber of Commerce Won’t Tell You About – Vince Staten (Harper & Row, NY, 1990)
Watch It Made in the USA -- Karen Axelrod & Bruce Brumberg (John Muir Press, 1997)
Plus:
“America: Why I Love Her” mural by Gary Sweeney, Denver International Airport
Specific sources for “Ratings and Rankings” category were:
America’s Most Charming Towns & Villages – Larry T. Brown (Open Road Publishing, Cold Spring Harbor, NY, 2004)
Best Small Towns – Norm Crampton (M. Evans and Company, NY, 2002)
Cities Ranked & Rated – Bert Sperling & Peter Sander (Wiley, Hoboken, 2004)
Fifty Fabulous Places to Raise a Family -- Lee Rosenberg & Saralee H. Rosenberg (Career Press, 1993)
Places Rated Almanac -- David Savageau & Geoffrey Loftus (Macmillan, 1997)
Retirement Places Rated – David Savageau (Wiley, Hoboken, 2004)
The 100 Best Art Towns in America – John Villani (The Countryman Press, Woodstock, VT, 2005)
The Great Towns of America – David Vokac (West Press, San Diego, 1998)
Main source for “Demographics” category was:
The Largest U.S. Cities Named After a Food and Other Mind-Boggling Geography Lists from Around the World – Brandt Maxwell (Santa Monica Press, Santa Monica, CA, 2004)