IV.

Domestic and International Trade

The first important American highways were water routes, and today they remain an integral component of the U.S. transportation network. Domestic shipping is composed of three types of services: ocean, Great Lakes, and inland waterways. Ocean shipping is divided into coastwise, intercoastal (that is, between Atlantic, Gulf, and Pacific ports), and noncontiguous trade (from the mainland to and from Alaska, Hawaii, Puerto Rico, and Guam).

Cargo moved in the domestic trades consists mainly of coal, iron ore, chemicals, petroleum and petroleum products, and agricultural products moving in bulk. Much of the intercity cargo is transported by vessels in the domestic service; in 1982, for example, more than 600 million tons of freight were carried by barges.

The U.S. is the world's largest trading nation, with 95 percent of its imports and exports (excluding trade with Canada and Mexico) moving by sea. Oceanborne foreign trade is conducted by three kinds of shipping service: liner or scheduled ships, nonliner tramp ships, and tanker service. In the mid-1980s this trade totaled about 677 million tons, valued at almost $303 billion.