Three that come to mind in Wisconsin -- well-regarded courses that fly well under the radar of most golf cognescenti -- are:
-- Big Foot CC, a Bendelow original dating back to 1924, with a funky par of 73 set on some wonderful rolling terrain near Lake Geneva;
-- Pine Hills CC in Sheboygan, which Tom Doak recently touted on his Instagram page, designed by the unknown Harry Smead and dating back to the 1930s. The course plays a large role in the development of Wisconsin as a golf mecca, as it's the course Herb Kohler wanted to buy when his guests at the American Club kept requesting a place to play a game. The club declined to sell, and Kohler embarked on his Blackwolf Run projects, which set off the run of modern-day courses that now dot the state. Under tournament conditions, widely viewed as one of the state's toughest courses.
-- North Shore CC, overlooking Lake Winnebago near Appleton, designed by another relatively unknown architect (Leonard Macomber), with recent work by Doak's Renaissance group.
I'd mention Langford's Spring Valley, near the Illinois border in rural Kenosha Co., but it's widely known here on the GCA board, if not by the broader audience of golfers. Still under-appreciated, and still the best golfing value in the state.