Canton families can depend on William J O'Brien Insurance to provide guidance and answer any questions. Servicing Canton and the entire Norfolk county region. William J. O'Brien Insurance Agency, Inc. is a full-service insurance agency, engaging in all lines of property.casualty and life insurance. They also offer a full line of financial services. The firm specializes in working with small to medium size businesses. The company was established in 1947 and incorporated in 1977 in Massachusetts.