The Maine Register state yearbook and legislative manual (black books) can be a good source. They contain info on all the towns and plantations etc. starting in the 1800s. You can find the postmaster, town selectmen, school committee members, clergy, you name it. You can find out when the town came into being, name changes and when other towns were annexed etc.
Don’t just look under the counties and towns. Scan through the first part of the books also. You’ll find custom districts, immigration departments, lighthouse districts and public health dept. info and some of the employees listed. Hopefully you can find these books stashed somewhere in a library. Some or all probably can be found on line as well.