In SC, you'll want to program talkgroups from the Palmetto 800 system to monitor SC Highway Patrol. Lots of info in the SC Wiki to determine which SCHP troops and Palmetto 800 sites to program.
At the very minimum, for Maryland, you will want the state police. You will need a good mobile antenna; their system is almost strictly a simplex 39 mhz system, except where the county's 800 system echoes it. See the wiki page for more information on that.
151.04/PL 173.8 (the audio is often overmodulated. The guy that runs that repeater should be fired...)
Frequencies for statewide, traffic office, districts 3,4,5 and 7