The County runs a DMV office, a relatively new prison, lots of health services and lots of social service programs, like managing medicaid.
The Essex County website is excellent. In addition to everything about the County, you will find a fantastic Geographic Information System (GIS) that is a treasure trove of historic and present facts and information about the County and each town: detailed tax maps, assessments, demographics, incomes, aerial and satellite photographs are just a sample of what is available.
There is a Directory of how to reach most government people at the town, county, state and Federal levels.
Perhaps the most important section is Essex County Board of Elections. Here, you can find out where to vote, how to run, how to register, how to get an absentee ballot, and who won. It is very easy to run for Keene Town Board for example – you need less than 20 signatures. There is contact information for both parties to help you figure everything out. Running for office is a great service to perform, even if you lose.
Each town in Essex County elects a Supervisor. The County is run the resulting collection of supervisors which is called the Board of Supervisors. The county site provides this link that sets up an email to the whole Board so you can easily provide them with your input to County issues. Board of Supervisors meeting minutes and resolutions are well indexed and easily searched.
The Civil Service Office handles job applications and HR issues for about 2000 county, town, village and school employees across the County.
The County Clerk office handles things like Dept of Motor Vehicles, gun permits, passports, hunting/fishing licenses, registry of land transactions, incorporation filings, handicapped parking permits, naturalization papers, tax liens, etc.
The County Dept of Public Works maintains some 350 miles of roads in 18 towns and 125 bridges. All bridges, except very short ones (under 30 feet?) are managed as county projects even if they are on town roads.