US Post Office is located at 300 E John St, Bay City, MI. This business specializes in Post Offices. US Post Office is open Mon, 9am-5pm; Tue, 9am-5pm; Wed, 9am-5pm; Thu, 9am-5pm; Fri, 9am-5pm; Sat, Closed; Sun, Closed and accepts American Express, Discover, Mastercard and Visa.