"[1] Many county collectors became interested in the pursuit after being given a school assignment to plot their travels on a county-outline map of the United States.
The club is a non-profit organization that meets annually in conjunction with the Automobile License Plate Collectors Association and recognizes completers (of which there are now 66, as of 2022) on its web site.
As of August 2022, the county collecting web site mob-rule.com has 7725 registered users from all 50 states, 9 provinces of Canada, and 26 other foreign countries.
Mathematician William J. Cook used the principles of the travelling salesman problem to calculate that the optimal route visiting every county's seat in the mainland United States would cover 93,466 miles (150,419 km), though he noted that county collectors typically travel a much longer distance.
[7] Ken Jennings discussed the phenomenon and the Extra Miler Club in his 2012 book, Maphead: Charting the Wide, Weird World of Geography Wonks'.