Mass C.O.P. is the largest law enforcement union in Massachusetts. Our focus on the welfare of our police officers and 911 police dispatchers has resulted in unprecedented membership growth. We now represent over 4,400 members serving in more than 173 Towns and Cities across our Commonwealth. Our long-term strategic planning and experienced staff has made us the most powerful and trusted law enforcement advocate in the Commonwealth of Massachusetts. Want to know more about who we are? Click here to learn about us and discover the benefits of being a part of Mass C.O.P.