I was looking up what 'HMU'  means on Urban Dictionary and I randomly decided to do a search for South Dakota. That turned out to be a funny decision. Here's the best definition I found.

Urban Dicitonary

Yes, I chose that one because whoever wrote it is confused about popularity versus population and they think Sioux Falls is the most civilized part of Sioux Falls. So I started clicking the related links. Here's what I got for Sioux Falls:

Urban Dictionary

Then Rapid City...

Urban Dictionary

And Brookings...

Urban Dictionary

They aren't the most accurate definitions, but aren't completely untrue either. Don't be offended. It's supposed to be funny.