Why doesn't coatesville pa have a mayor?

Coatesville, PA does not have a mayor because it is governed by a City Council with seven members. There are 5 members who represent one of each of the five wards, and 2 members who are "at large". Each council person serves a four year term and the elections are staggered so that four members will be up for election at one time, and two years later the other three.