From the Document: "On April 4, 2019, foreign ministers from the 29 member states of the North Atlantic Treaty Organization (NATO) are to gather in Washington, DC, to mark the 70th anniversary of the North Atlantic Treaty (also known as the Washington Treaty). NATO Secretary General Jens Stoltenberg is to address a joint session of Congress on April 3, 2019, the first ever to do so. Congress was instrumental in creating NATO in 1949 and has played a critical role in shaping U.S. policy toward the alliance ever since."
CRS Report for Congress, R45652
Congressional Research Service: https://crsreports.congress.gov/