That's the beauty of Chirp, it connects to several common databases, Repeaterbook (for ham), Radio Reference (for others), etc. so it can populate the file for you. The DBs can't tell you which ones are active but at least you can fill the file easily.
Look under Radio->Import from data source->Repeaterbook and it'll give you an option to populate based on proximity (place plus distance) or political boundaries (State and county).
It also has some standards you can plop in such as ARRL recommended calling frequencies, NOAA NWS frequencies, etc.
I only have very old RT Systems (like version 3) applications that IIRC had to be done importing them in CSV or XLS files or the ARRL TravelPlus CD-ROM (that's how old mine are!). By now surely they'd integrate the ability to read them from online databases.