The Frontier Boys in Hawaii, or The Mystery of the Hollow Mountain, (Paperback)

The Frontier Boys series was a popular adventure series for young readers published in the early 1900s. It follows a group of teenage boys who travel across different rugged frontiers, getting into various exciting and often dangerous adventures.

The books are set in different parts of the world, from the American West to Alaska and even other global locations. The stories focus on themes of bravery, teamwork, and the frontier spirit, where the boys must rely on their skills, wits, and each other to navigate the challenges they face.

Some of the titles in the series include The Frontier Boys on Overland Trail, The Frontier Boys in the Grand Canyon, and The Frontier Boys in the Rockies. The series was known for its fast-paced action and appeal to young readers interested in adventure and exploration during the time it was published.