There are many places in the states where low band skip can originate. 33.9 is a very busy freq. with lots of EMS and firecalls on it. The 42 Mhz range is full of state police, as is the 39 MHz range. And there are local or county PDs, fire and EMS sprinkled in there as well.
The state police that I know about that still use low band in the states are: Illinois, Missouri, Mississippi, North Carolina, California, Indiana (to a lesser degree) and Maryland. Maryland uses the 39 MHz range, as does Calif. Indiana, Illinois and Missouri use the 42 MHz range. I keep 42.60 (Illinois state police in Joliet) in my radio at all times as it's one of those that's a "frequent flyer".
I'm sure the state listings on this site will give you some insights. However, you may be hearing a fire or EMS agency that is local to someplace and that may require some research and searching google, etc. If you have a CTCSS/DCS-capable scanner that decodes instantly, like the Pro-96 or the Uniden 396, that will prove invaluable as the code in use will help you narrow it down quickly as does determining what kind of southern drawl (if any) the dispatcher has.
Don't forget that the U.S. (and Canadian) military use a lot of low band too. When I lived in Kingston, Ontario, I regularly received Ft. Hood, Texas range control on 30.45. Just yesterday, Ft. Drum's (NY) range control on 38.5 was logged in North Carolina. And I know Canforces Petawawa uses several low band freqs for its range controls. Sometimes figuring out who you're hearing takes a while. And we haven't even mentioned the US military aircraft that still use low band or offshore/overseas users.
Happy listening!