In some areas the DB is nearly useless. There aren't people everywhere that identify and submit things.
Go to your county page, click the menu button on the upper right part of the page and select
FCC Licenses.
You should get a page like this.
FCC Licenses in Wichita County, Texas (TX)
www.radioreference.com
The column headings are sortable. On the left there is a search box that says
Choose Licenses to Filter Out/Remove. At first it's probably best to filter out Expired/Cancelled licenses. The Search box on the right is good for finding frequencies, licensee names, cities.
Click on the callsigns for more detail.
It helps if you are familiar with the codes used on the licenses.
wiki.radioreference.com
wiki.radioreference.com
wiki.radioreference.com
I don't know anything about South Carolina but they have a statewide P25 trunked system
Palmetto 800 Trunking System Profile
www.radioreference.com
I don't know how many county and local users are on it. Maybe yours are.