Complex sentence: At the age of 14, Kit was apprenticed to a saddlemaker (Workman's Saddleshop) in Franklin, Missouri, which was situated at the eastern end of the Santa Fe Trail, which had opened two years earlier.
Split into simpler sentences: At the age of 14, Kit was apprenticed to a saddlemaker (Workman's Saddleshop) in Franklin. The town was the eastern terminus of the Santa Fe Trail, which had opened two years earlier.