Lillian Ruth Hruda Peterson, a resident of Ridgefield Crossings, died Tuesday, Nov. 12. She was 90.

Born in Chicago, Ill., to Joseph Hruda and Lillian Houdek Hruda, she graduated from the University of Illinois in 1945 with a master of science in chemistry. She first worked as an organic research chemist for the Armour Research Foundation in Chicago from 1945 to 1951.

She married in 1948 to Richard Allen Peterson and divorced in 1978. She returned to full-time work in 1971 as a high school mathematics and computer science teacher in Wilmington, Del., until she retired.

Ms. Peterson was active in the founding of the Newark, Del., Fellowship for Unitarian Universalists and volunteered for many years at the Hockessin branch of the New Castle County, Del. library.

She is survived by five children: Barbara Lynn Hruda of Newark, Lawrence Scott Peterson of Las Vegas, Nev., Eric Bruce Peterson of Evanston, Ill., Stephen Kurt Peterson of Newark, and Carla Laurie Peterson Kahlbaugh of Danbury,  as well as several grandchildren and great-grandchildren.