Doris Polsky, 90, co-founder of a real estate firm that was instrumental in the successful integration of Mt. Airy, died June 3 at her home in Mt. Airy.

Mrs. Polsky and her twin sister, the late Shirley Melvin, opened Twin Realty in Germantown in 1965, at a time when banks and mortgage companies were redlining sections of Northwest Philadelphia and unscrupulous real estate brokers were attempting to induce panic selling by white homeowners.

To combat these practices, the sisters sought like-minded people and asked them to throw welcoming parties for their new black neighbors. They sold homes to people of all colors, creeds and sexual orientation.

As a result of their efforts, Mt. Airy has been recognized by the U.S. Department of Housing and Urban Development as one of the nation’s best integrated communities. For their work in integrating Mt. Airy, they were recipients in 2004 of the Human Rights Award for Community Service given by the Philadelphia Commission on Human Relations.

The sisters had helped to found Allens Lane Art Center and West Mt. Airy Neighbors. Mrs. Polsky retired from Twin Realty in 1991 when the firm merged with Wissahickon Realty, but her sister continued until 2008. Mrs. Melvin died in 2009.

Mrs. Polsky and her sister were born in the Grays Ferry section of Philadelphia and graduated from the Philadelphia High School for Girls. Precocious mathematicians, the sisters were recruited while students at the University of Pennsylvania to work on Army ballistics research during World War II. They were also asked by the Army to program the differential analyzer, a mechanical calculator that could reduce 40 hours of an individual’s mathematical work to 15 minutes.

Mrs. Polsky is survived by sons Scott and Steven; daughters Joan, Lisa and Ellen; 12 grandchildren, and one great-grandchild. Her husband, Samuel Polsky, died in 1975. – WF