Town Hall Address 515 Watchung Ave. Plainfield, NJ 07061 United States- Union County Website https://www.plainfieldnj.gov/ County Clerk 908-753-3222 515 Watchung Ave. Plainfield, NJ 07061 United States County Admin 908-226-2571 Plainfield, NJ 07061 United States Assessor 908-753-3203 515 Watchung Ave. Plainfield, NJ 07061 United States Tax Collector 908-753-3214 515 Watchung Ave. Plainfield, NJ 07061 United States Town Hall Hours Monday - Friday: 9:00 A.M. - 5:00 P.M. County Union