US Post Office is located at 12 Main St, Marathon, NY. This business specializes in Post Offices. US Post Office is open Mon, 8am-5pm ; Tue, 8am-5pm ; Wed, 8am-5pm ; Thu, 8am-5pm ; Fri, 8am-5pm ; Sat, 8am-12pm ; Sun, Closed. and accepts American Express, Discover and Visa.