Complex sentence: Further, the post was located deep within a several hundred mile stretch of the Missouri River known as the Missouri Breaks, where the steeply eroded badlands along the river it from the surrounding eastern Montana plains.
Split into simpler sentences: Further, the post was located deep within a several hundred mile stretch of the Missouri River known as the Missouri Breaks. The breaks were steeply eroded badlands bordering the river and separating it from the surrounding eastern Montana plains.