Mayoralty in the United States
In the United States, there are several distinct types of mayors, depending on the system of local government. Joseph P. Riley, Jr. has been in office longer than any other sitting city mayor in the United States.
Types of mayoralty 
Under council-manager government, the mayor is a first among equals on the city council, analogous to a head of state for the city. He or she may chair the city council, lacking any special legislative powers, but in most cases able to set the legislative agenda. The mayor and city council serve part-time, with day-to-day administration in the hands of a professional city manager. The system is most common among medium sized cities from around 25,000 to several hundred thousand, usually rural and suburban municipalities.
In the second form, known as mayor-council government, the mayoralty and city council are separate offices. Under a strong mayor system, the mayor acts as an elected executive with the city council functioning with legislative powers. He or she may select a chief administrative officer to oversee the different departments. This is the system used in most of the United States' large cities, primarily because mayors serve full-time and have a wide range of services that they oversee. In a weak mayor or ceremonial mayor system, the mayor has appointing power for department heads but is subject to checks by the city council, sharing both executive and legislative duties with the council. This is common for smaller cities, especially in New England. Charlotte, North Carolina and Minneapolis, Minnesota are two notable large cities with a ceremonial mayor.