According to her birth record, Mary Rose Crehan was born in Pittsburgh on August 31, 1908. Her parents, residents of Haldane Street, Pittsburgh, were Wiliam E. Crehan, a policeman born in Pittsburgh, and Margaret Kennedy, born in Kittaning, Armstrong County.

In the 1910 Federal Census of Pittsburgh, William Crehan, a City Policeman, and his wife, Margaret, lived on Winterburn Street. Mrs. Crehan had given birth to 6 children, all of whom were living. They were: William, 13, John A., 11, Mes [Mercedes], 8, Margaret, 6, Catherine, 4, and Mary, 1 1/2.

On September 7, 1910, a few months after the census enumeration, the mother, Margaret G. Kennedy Crehan, died. She was 36 years old. At that time, the family lived at Gladstone & Biglow, Pittsburgh.

In the 1920 census, Mary Crehan, 10, and her sister, Catherine, 12, were living at the House of the Good Shepherd, Lincoln Avenue, Pittsburgh.

In 1930, Mary was a student nurse at St. Francis.

In 1940, Mary R., a "Nurse - Medical," was living in a home on Haldane Street with her sister, Catherine Rapp, and Catherine's husband and child.

Mary Rose Crehan served in the Army Nurse Corps during World War II, from March 15, 1945 until December 9, 1945. When she entered service, she lived on Haldane Street in Pittsburgh. She still resided there when she applied for Veteran Compensation in 1950.

2nd Lieutenant Mary Rose Crehan died on June 2, 1986 and is buried at Saint Francis Cemetery, Phoenix, Maricopa County, Arizona. Her grave has a military marker.