Jon Kest, 57, a social activist and founder of the Philadelphia chapter of the Association of Community Organizations for Reform Now (ACORN), died Wednesday, Dec. 5, of liver cancer at his home in Brooklyn, N.Y.

Born in New York City, Mr. Kest graduated from the University of Pennsylvania in 1977 with a bachelor's degree in history. He remained in Philadelphia after his graduation and became an advocate for the less fortunate.

Through his work with ACORN, in conjunction with the Kensington Joint Action Council, Mr. Kest led an effort to transfer the titles of abandoned houses to low-income families in the early 1980s. He also lobbied for neighborhood-improvement campaigns and increased service from SEPTA.

"He was really a brilliant guy whose work made major changes to how we think about community organization and social change," said Bruce Dorpalen, a friend, who had met Mr. Kest through ACORN Philadelphia.

After returning to New York City in the early 1980s, Mr. Kest founded the Working Families Party and most recently held the position of director of New York Communities of Change.

Weeks before his death, Mr. Kest grieved the loss of his daughter, Jessie, 24, who was fatally injured Oct. 29 when she was struck by a fallen tree during Hurricane Sandy.

He is survived by his wife, Fran Streich; a son, Jake Streich-Kest; and a brother.

A memorial service will be at 10:30 a.m. Sunday, Dec. 9, at the United Federation of Teachers headquarters, 52 Broadway, New York City.