This portrait of the second Secretary-General Dag Hammarskjöld was painted by Argentine artist, Mrs. Celina D.M. de Mundin Schaffter. 

Dag Hammarskjöld was a Swedish economist and diplomat who served as Secretary-General of the United Nations from 1953 until his death in 1961. While en route to cease-fire negotiations in Northern Rhodesia, present day Zambia, during the Congo Crisis his airplane crashed, killing the Secretary-General and 15 staff-members and peacekeepers traveling with him. He was 56 and considered one of the best statesmen in the diplomatic community and beyond. In 1963, a book was published entitled Markings (Vagmaken) which is a collection of his journal contemplations.  
He was posthumously awarded with the Nobel Peace Prize in 1961, having been nominated before his passing. 

The portrait was a joint gift from the Governments of Sweden and Argentina to the United Nations.