What's your breaking point for fuel costs this summer? Will you stay out of the National Park System if you have to pay more than $4.50 per gallon, or $5 per gallon?

Almost 15 million Canadians and more than 3.5 million Americans live within a three-hour drive of Thousand Islands National Park and more than 35,000 vehicles pass by it daily on Hwy. 401, but the Ontario park only sees about 80,000 visitors a year.

A road trip of roughly 2,500 miles led me to four intriguing units of the National Park System that, while not at the top of everyone's go-to list, revealed both rich and troubling chapters of American history that likely would have faded into irrelevance without the parks that interpret their stories.

On route to an old-growth Eastern hemlock stand, we’re waylaid by a hiker keen to share her sighting of a Lady’s Slipper, a prolific orchid with a pink, pouch-shaped flower that she has confused with the rare Hooker’s orchid the park wants citizen scientists to keep an eye out for. We pause to admire ruby red teaberries and bunchberries with tiny but showy white “flowers” made up of four oval bracts, rub sweetfern to inhale its namesake scent, and gently finger the ragged lung lichen that proliferate on tree trunks.