Since you indicate you are in Gadsden, these are the frequencies in use there:
158.790 - Dispatch
159.030 - Car-to-post
You may also catch some stuff on these:
155.010 - State net
155.475 - National law enforcement interop. It's also used as a general car-to-car frequency by the troopers in some areas (such as Quad city's). They may also use the dispatch frequency as a car-to-car channel (like in Hamilton).
Just so you know, you likely won't be hearing many of the mobile units as the DPS doesn't use repeaters. Depending on your antenna setup and your elevation, you will probably only hear units within 5 miles or so of you.