Sister Mary William Posthauer, O.P., a member of the Sisters of St. Dominic, Amityville, L.I., for 81 years, died June 25.  She was 99.

Born as Agnes in College Point, she lived in St. Fidelis parish.  She attended St. Agnes Academy but in her second year transferred to the newly formed Dominican Sisters Juniorate in Watermill, L.I.

She was in the first graduating class and entered the novitiate in Amityville in 1935. She pronounced her final vows in 1936.

She taught at St. Margaret’s, Middle Village; and Sacred Heart, East Glendale.

She taught Spanish and English at Dominican Commercial H.S., Jamaica, 1948-66, and then joined the faculty Molloy College, Rockville Centre.

After receiving her doctorate in education from Columbia University, she earned grants for further study at Fairfield University, Conn.; Temple University, Pa.; and Catholic University in Valencia, Spain. There she also became involved with Peace Corps volunteers who were required to learn Swahili.

She later became academic dean at Molloy.

From 1982 to 1988, she was principal at Holy Redeemer School, Freeport, L.I. While there, she served both the children and the adult Spanish-speaking parishioners.

In 1988 she was asked by the congregation to serve in Amityville as director of Sisters’ studies. She also served as religious education coordinator at Our Lady of the Miraculous Medal parish, Point Lookout, L.I.  Subsequently, she became a religious education instructor with extra duties at St. Matthew parish, Dix Hills, L.I.

When Dominican Village Retirement and Assisted Living Community opened in 1992, she signed on as a volunteer to teach the residents Spanish and line dancing and produced a newsletter for which she did all of the photography. When her sight became impaired, she began special sessions for the residents with low vision and made personal visits to the residents.

At the same time she became active in both the Dominican Village Civic Association and that of North Amityville until she could no longer continue because of near blindness and hearing loss.

She was honored publicly by her Amityville Dominicans in a yearly gala event, held at the Garden City Hotel, as an extraordinary member of the Congregation and of the larger community who embodied the best of the Dominican tradition.

Additionally, she was honored by the Dominican Village Board of Directors as a treasured volunteer and a source of inspiration and encouragement to the residents.

Burial was in the Sisters’ cemetery in Amityville.