Colorado Springs couple Mike and Donna Guthrie were looking for an idea for a new trip. They were edging toward 70 and wanted to do something big. 

Rather than voyaging to Europe or Asia for a far-off adventure, they turned their attention to the national parks. But not just any national park — all of them! 

“You know, there’s a lot of America we haven’t seen,” Donna told her husband according to The Gazette newspaper in Colorado Springs.

Seven years later and the Guthrie’s celebrated their 59th and final national park at the Great Smoky Mountains on the year of the Park Service 100th anniversary.

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There were rules to their adventure, however. For starters, the 10 national parks they’d visited already wouldn’t count. They would repeat those again. They also agreed that they would have to get a picture by each park entrance, speak with a ranger and cover at least five miles on foot.

“There are different stages in marriage. Our kids are grown now; now we’re into the grandparent stage,” Donna told the Gazette before pausing. “I think this has been really fun for us as a couple.”