1·First came the steamboat; although flatboats and keelboats continued to be important until the 1850's steamboats eventually superseded all other craft in the carrying of passengers and freight.
首先是蒸汽船，虽然1850年时蒸汽船最终取代了所有用来运载乘客和货物的船只，随后平底船和龙骨船仍然相当重要。
2·Keelboats, flatboats, and large rafts carried the first major commerce.
运货船、平底船和大木筏运载着最初的主要商品。