A riverboat is a watercraft designed for inland navigation on lakes, rivers, and artificial waterways. They are generally equipped and outfitted as work boats in one of the carrying trades, for freight or people transport, including luxury units constructed for entertainment enterprises, such as lake or harbour tour boats. As larger water craft, virtually all riverboats are especially designed and constructed, or alternatively, constructed with special-purpose features that optimize them as riverine or lake service craft, for instance, dredgers, survey boats, fisheries management craft, fireboats and law enforcement patrol craft. Design differences Riverboats are usually less sturdy than ships built for the open seas, with limited navigational and rescue equipment, as they do not have to withstand the high winds or large waves characteristic to large lakes, seas or oceans. They can thus be built from light composite materials. They are limited in size by width and depth of the river as well as the height of bridges spanning the river. They can be designed with shallow drafts, as were the paddle wheel steamers on the Mississippi River that could operate in water under two metres deep. While a ferry is often used to cross a river, a riverboat is used to travel along the course of the river, while carrying passengers or cargo, or both, for revenue. (Vessels like 'riverboat casinos' are not considered here, as they are essentially stationary.) The significance of riverboats is dependent on the number of navigable rivers and channels as well as the condition of the road and rail network. Generally speaking, riverboats provide slow but cheap transport especially suited for bulk cargo and containers. History As early as 20,000 BC people started fishing in rivers and lakes using rafts and dugouts. Roman sources dated 50 BC mention extensive transportation of goods and people on the river Rhine. Upstream, boats were usually powered by sails or oars. In the Middle Ages, towpaths were built along most waterways to use working animals or people to pull riverboats. In the 19th century, steamboats became common. The most famous riverboats were on the rivers of the midwestern and central southern United States, on the Mississippi, Ohio and Missouri rivers in the early 19th century. Out west, riverboats were common transportation on the Colorado, Columbia, and Sacramento rivers. These American riverboats were designed to draw very little water, and in fact it was commonly said that they could