The Kennebec River, Maine's largest river, rises at Moosehead Lake and flows 190 miles through Somerset, Kennebec, and Sagadahoc Counties to the Gulf of Maine at Popham Beach. For over 40,000 years before European arrival, it was a primary travel route for Native Americans. Samuel de Champlain explored the area in 1604-1607, and George Popham established the short-lived colony of Fort St. George at the river's mouth. In 1775 Benedict Arnold chose the Kennebec River for his march into Canada. The river then became a gateway for European trade and settlement, carrying lumber, pulp, and ice to the coast in exchange for finished goods needed by colonists, while shipbuilding flourished along its banks. Over the years it also provided power for mills and continues to be an important source of hydroelectric power and recreation, particularly white water rafting.