 Since its foundation, the city has expanded from the mouth of Sullivans Cove in a generally north-south direction along both banks of the River Derwent, from 22 km inland from the estuary at Storm Bay to the point where the river reverts to fresh water at Bridgewater.Penal transportation ended in the 1850s, after which the city experienced periods of growth and decline.The early 20th century saw an economic boom on the back of mining, agriculture and other primary industries, and the loss of men who served in the world wars was counteracted by an influx of immigration.