Francesca Dekum Mills attended Miss Catlan's School in Portland, Oregon and graduated from Reed College in 1929.

After Mills was appointed a Foreign Service officer in the Department of State in 1928, he began a diplomatic career that spanned 32 years.

During Sheldon Mills' time in Kabul, King Zahir Shah received economic development support from both the United States and the Soviet Union which was an unusual achievement during the Cold War when recipient countries were clients of one super power or the other.

In Jordan, Mills enjoyed a good personal interaction with King Hussein which enhanced the United States-Jordanian relationship.

According to Nigel Ashton's, "King Hussein of Jordan, a Political Life," (page 83) the King told Ambassador Mills in early 1960 that, 'the Arab legend,' that Israel should be pushed into the sea should be abandoned, and that "It was time to put aside emotionalism and take steps toward a final settlement between Israel and the Arabs."