Complex sentence: They had traveled from western Outagamie County on the Wolf River during the summer of 1857, making their way to the mouth of the Shioc River and moving to a spot where the Black Creek flows into the Shioc.
Split into simpler sentences: They had traveled from western Outagamie County on the Wolf River during the summer of 1857 and made their way to the mouth of the Shioc River. They then moved to a spot where the Black Creek flows into the Shioc.