Irving Bluestone, former United Auto Workers union leader and assistant to founding president Walter Reuther, has died at age 90.

Bluestone, whose career with the UAW spanned five decades, suffered heart failure and died at his Massachussetts home Nov. 17.

“He was a passionate fighter for working men and women everywhere and his contributions to the cause of social justice will be remembered for many years to come,” UAW President Ron Gettelfinger says in a message posted to the union’s website.

Bluestone’s roots with the union stretch back to 1945 when he was appointed to its national staff. From 1947 through 1961, he played key supporting roles in the UAW’s negotiations with General Motors Corp.

From 1961 to 1970, Bluestone served as Reuther’s administrative assistant. Following Reuther’s death in a 1970 plane crash, he was named head of the UAW’s GM department. He retired in 1980.