Complex sentence: Yount began constructing a winter camp at the junction of the East Fork of the Yellowstone River (now known as the Lamar River) and Soda Butte Valley, a location he chose because it allowed him to protect herds of buffalo and elk against poachers.
Split into simpler sentences: Yount began constructing a winter camp at the junction of the East Fork of the Yellowstone River (now known as the Lamar River), and Soda Butte Valley. He selected this location because it allowed him to protect herds of buffalo and elk against poachers.