self-supporting corporate agency formed in 1921 by agreement between the states of New York and New Jersey for the purpose of developing and operating trade and transportation facilities in the northern New Jersey–New York City region. Twelve nonsalaried commissioners, six appointed by the governor of each state, plan and oversee the operations of a variety of services and facilities. This responsibility includes the maintenance and management of the Lincoln (Lincoln Tunnel) and Holland (Holland Tunnel) tunnels under the Hudson River and of the bridges linking the two states. Kennedy, Newark, La Guardia, and Teterboro airports also are under the jurisdiction of the Port Authority, as are three bus-truck terminals, seven marine passenger ports, and a heliport. During the 1970s the Port Authority constructed the twin-towered World Trade Center in Lower Manhattan to house firms and agencies engaged in international trade in an effort to further encourage commerce in the region; both towers were destroyed in a terrorist attack in 2001.