Bay City is a city in Tillamook County, Oregon, United States. The population was 1,286 at the 2010 census. According to the United St…Bay City is a city in Tillamook County, Oregon, United States. The population was 1,286 at the 2010 census. According to the United States Census Bureau, the city has a total area of 1.62 square miles, of which 1.26 square miles is land and 0.36 square miles is water.