The Pony Rider Boys in New England - Frank Gee Patchin

Yee-Haw! The Pony Rider Boys are on the trail again! This time the boys are doing something a little different. Instead of heading west to the wide open spaces, they are riding east to the Wilderness of Maine. But, as always, trouble finds the boys, in both the four-legged and two-legged form! Will they make it back out of the wilderness? - Summary by Ann Boulais

Previous book in the series: The Pony Rider Boys on the Blue Ridge
Next book in the series: The Pony Rider Boys in Louisiana