Ralph Allison Simmons, a retired civil engineer who had been active in civic endeavors in Talbot County, died Thursday of amyotrophic lateral sclerosis, or Lou Gehrig's disease, at Fairhaven retirement community in Sykesville, his home for the past five years. He was 75 and formerly lived in St. Michaels.

Before his retirement in 1975, he had been assistant director for computer sciences at the Commerce Department's National Bureau of Standards in Gaithersburg. He had also been a Pennsylvania Railroad civil engineer and worked in defense intelligence.

Born in St. Paul, Minn., he grew up in College Park and earned a degree in civil engineering from the University of Maryland. He served in the Navy from 1945 to 1947.

Mr. Simmons served on the St. Michaels utility commission and the town's board of zoning appeals. He was also a member of the Talbot County Planning and Zoning Commission and a board member and treasurer of the Chesapeake Bay Maritime Museum.

Services will be held at 2 p.m. Sunday at Christ Episcopal Church in St. Michaels, where he had been a vestryman and senior warden.

He is survived by his wife of one year, the former Mary Honsberger; two sons, Ralph A. Simmons of Great Falls, Va., and Robert W. Simmons of Iron Station, N.C.; a daughter, Barbara Unkle of Oceanport, N.J.; and nine grandchildren. His first wife, Ann Boswell, died last year.