Mugar was born March 5, 1901, in Kharpert (Harpoot)[1] in the Mamuret-ul-Aziz Vilayet of the Ottoman Empire (present-day Turkey), of Armenian parents.

The 1910 United States census shows the family in the 19th Ward of Boston and lists Sarkis Mugar's occupation as "waiter in restaurant."

After the war ended and wartime restrictions and shortages were over, Stephen worked with his younger cousin John M. Mugar to expand Star Market throughout Greater Boston to meet the increased affluence and consumer demand.

After making his fortune in the Star Market business, Stephen P. Mugar became a generous contributor to educational institutions and Armenian causes locally and abroad.

These include: The Armenian Assembly of America is a non-profit group aimed at increased Armenian-American participation in the American democratic process as well as assisting in humanitarian and development programs in Armenia.

In 1992, the former Coolidge Bank building in Watertown, which was bought by the Armenian Library and Museum of America in 1988, was dedicated to the memory of Stephen and Marian Mugar.

[4] In 2002, David Mugar gave $5 million to the Cape Cod Hospital in Hyannis for a new four story wing in memory of Marian and Stephen.