Board of supervisors
A board of supervisors is a governing body that oversees the operation of county government in all U.S. counties in Arizona, California, Iowa, Mississippi, Virginia, and Wisconsin as well as 16 counties in New York. There are equivalent agencies in other states.
Similar to a city council, a board of supervisors has legislative, executive, and quasi-judicial powers. The important difference is that a county is an administrative division of a state, whereas a city is a municipal corporation; thus, counties implement and, as necessary, refine the local application of state law and public policy, while cities produce and implement their own local laws and public policy (subject to the overriding authority of state law).
Legislative powers
Boards may pass and repeal laws, generally called ordinances. Depending on the state, and the subject matter of the law, these laws may apply to the entire county or to only unincorporated areas not within the jurisdiction of a city. The board is also responsible for approving the county budget. County governments may collect state taxes and, in some states, they may also levy taxes, such as property or sales tax.