Behr served in the United States Navy during World War II, joining in 1941 and being discharged in 1946.

After leaving the Senate he remained active as an environmental protection activist in California.

A street adjacent to the Marin County Civic Center and a scenic overlook at Drakes Beach in the Point Reyes National Seashore are named in Behr's honor.

The "Lifetime Achievement Award" of the Marin Conservation League[2] and the "Peter Behr Steward of the Land Award" of the Environmental Action Committee of West Marin are named in his honor.

[3] Behr died on March 10, 1997, at Marin General Hospital in Greenbrae, California, aged 81, after battling Parkinson's disease for six years.