Mercy Sister Mary Brian Costello, 98, died May 22 at Mercy Circle.

Sister Brian entered the Sisters of Mercy in 1942 and received her bachelor’s degree from Saint Xavier University and her master’s degree from the University of Notre Dame. 

She served in various educational ministries as both teacher and as a school administrator, including as principal of Mother McAuley Liberal Arts High School.  

She served on the Sisters of Mercy Leadership Team from 1973 to 1979. In 1983, Sister Brian was named the first woman and non-cleric superintendent of schools for the Archdiocese of Chicago.  In 1989, Cardinal Joseph Bernardin named Sister Brian his chief of staff, a pioneering position for a woman and one she held until she retired in 1997.

Throughout her ministry, Sister Brian exhibited a passion for assuring educational opportunities for all children. She was a founding member of the Big Shoulders Fund.