 Population expansion of the state has followed the path of the early waterways, first the Hudson River and Mohawk River, then the Erie Canal.In the 19th century, railroads were constructed along the river valleys, followed by the New York State Thruway in the 20th century.The New York State Department of Transportation (NYSDOT) is the department of the government of New York responsible for the development and operation of highways, railroads, mass transit systems, ports, waterways, and aviation facilities within New York State.