In U.S. local government within a U.S. state there are both what are called "general purpose governments" like counties, New England towns, townships, and municipalities, and what are called "special district governments" consisting in part of school districts, and in part, of special purpose governmental entities such the Chicago Transit Authority, or a mosquito protection district or a business development district.
As of 2017, according to the U.S. Census of Governments, there were 38,542 special district governments in the United States that are not school districts, out of 90,126 state and local governments of any kind in the United States (about 43% of all governments in the United States). It explains that:
Local governments are classified into five types: county, municipal, township, special districts and school districts.
County, municipal and township governments are general-purpose governments. The official count for those types of governments has not changed significantly since 2012.
Then there are special districts. They typically have a shorter lifespan and higher turnover than general purpose governments, but the difference in their counts was also relatively slim between 2012 and 2017: The 2017 Census of Governments added more than 1,500 special districts and removed roughly 1,260 that are no longer operating.
This question concerns special district governments, other than K-12 level school boards, in U.S. states (I omit from the question special districts in U.S. territories and possessions which present some definitional issues not present in U.S. states).
Some of these special district governments have elected boards of directors and/or other elected officials elected by members of the general public, but most of them have an appointed board of directors. The appointed board members of special district governments are usually appointed by one or more other governmental entities, or by a court, or for example, by owners of business property in a business development district.
I would like to know how many of the 38,542 special district governments in the U.S. other than school boards have elected officials, and how many officials are elected to these governments. But, the U.S. government census of local governments does not provide this information (at least in an easily accessible manner).
Among other reasons, this is interesting because it goes to the source of the "long ballot" in the U.S., to the amount of information about government that a voter needs to know to be well informed, to better understand the make up of the "minor league" of politics that can serve as a training ground for high political offices later in the career of those politicians, and to judge how much "hands on" involvement voters in the U.S. is in local government.