Rockland is a city in Knox County, Maine, in the United States. It is the county seat of Knox County. The city is a popular tourist destination. It is a departure point for the Maine State Ferry Service to the islands of Penobscot Bay: Vinalhaven, North Haven and Matinicus. Rockland developed rapidly because of shipbuilding and lime production. In 1854 alone, the city built eleven ships, three barks, six brigs and four schooners. The city had twelve lime quarries and 125 lime kilns, with upwards of 300 vessels to transport the mineral to various ports in the country.