Post office in Halfway (Maryland) Find any Post office in Halfway, Maryland. Addresses, phone numbers, working hours and other information. Quick go: All types of places Bus station Car wash Establishment Food Gym Health Meal delivery Meal takeaway Post office Transit station US POSTAL SERVICE mail Box. Establishment, Post office Halfway, Halfway, MD 21740 Types of places All types Bus station Car wash Establishment Food Gym Health Meal delivery Meal takeaway Post office Transit station