I recall few that were really memorable, but there are some:
Santa Fe, New Mexico
Sedona, Arizona
Bemidji, Minnesota
Barrow, Alaska
Those all must count as small I suppose, for medium I'd offer,
Louisville, Kentucky
Madison, Wisconsin
Santa Barbara, California
I don't really know how to categorize Boise, Idaho and Park City, Utah but they are two of my favorite American small cities, though they both have features of much larger places.