N.Y. Bridges & Tunnels New York-New Jersey Law § 14
The construction, maintenance and operation of vehicular bridges and tunnels within the said port of New York district (including the said Holland tunnel and the said Midtown Hudson tunnel), are and will be in all respects for the benefit of the people of the states of New York and New Jersey, for the increase of their commerce and prosperity and for the improvement of their health and living conditions; and the port authority shall be regarded as performing an essential governmental function in undertaking the construction, maintenance and operation thereof and in carrying out the provisions of law relating thereto, and shall be required to pay no taxes or assessments upon any of the property acquired or used by it for such purposes.
N.Y. Bridges and Tunnels New York-New Jersey Law § 14