William Henry Jackson's short life as a bullwhacker quickly convinced him that that was not the career for him.

A billiards table offering one of the few respites from the daily hardships endured by soldiers on the frontier in the wake of the Civil War could not temper the racism that some white troops harbored against their Black peers.

There are few outward signs that Ocmulgee Mounds National Historical Park is tucked into the middle of Macon, Georgia, surrounded by residential and commercial development. My family and I nearly drove past the entrance as our heads moved from the phone directions to the road and back again. But as soon as we followed the signature national park signs, it felt like a curtain of greenery wrapped itself around our car. We could hear sounds of the city, but all we saw were shades of emerald.

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.