Traveling to all 50 states in the U.S. is kid stuff. Members of the Extra Milers Club go, well, the extra mile. Their goal is to visit every county or equivalent jurisdiction in the U.S., a total of 3,143 as of July 1, 2013.

Thirty-four people in the club’s 31-year history have reached 100 percent, including Marge Brown, the most recent finisher who completed the quest on her 76th birthday in 2013.

County collecting is a strange hobby, but it’s one that keeps you on the move. Reid Williamson (final jurisdiction: Aleutians East Borough, Alaska) has been interested in counties for more than 50 years. “When I was about 10 years old, my father used an atlas to show me where my uncle was living in Arizona,” the self-described “list keeper” says. “The map was the kind from 1940s that had very vividly marked county lines. When I was 14, my aunt gave me another atlas that I promptly started desecrating by marking the counties that I had been to.”

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He joined the Extra Milers in 1991 after a chance meeting with one of the co-founders in the parking lot at the Grand Canyon. The two knew of each other from the License Plate Collectors club, to which they both belonged.

Williamson completed his journey at Dutch Harbor in Alaska in 2007. He is now 74 percent of the way through his quest to become the first person to visit all 3,143 counties twice.