The Hill People, also referred to as "the people in the hills," are a group of unknown individuals that live in the hills above the Forty , the people that Cueball and Megan belong to.  Both groups live along the same river, which occasionally carries Hill People objects (likely lumber and building supplies) downstream to the latter group.  Megan mentions to the Beanie leader that the Hill People don't like the Forty.  It has been speculated on the One True Thread that this animosity might be due to the Forty's penchant for repurposing Hill People items, but the comic does not confirm this as of yet.