Why did the Corps of discovery split into two groups on their way back to Missouri?

The Corps of Discovery split into two groups on their return to Missouri primarily to expedite their journey and explore more territory. One group, led by Captain Lewis, took a more direct route along the north side of the Missouri River, while Captain Clark's group traveled along the south side. This division allowed them to cover more ground and gather additional information about the regions they had explored. The split also enabled them to conduct separate surveys and map different areas effectively.