A statement on the singer-songwriter's website revealed that McKenzie died on Saturday in Los Angeles. He suffered from Guillain-Barre Syndrome, a disease that affects the nervous system, and had been in and out of the hospital since 2010. McKenzie had been very ill as of late, according to the statement.
"San Francisco'' was written by John Phillips, the leader of the 1960s group The Mamas and the Papas. But McKenzie sang it and it has stood as an anthem for the 1960s counterculture movement. The song later appeared on the 1994 soundtrack to "Forrest Gump."
"I am amazed at how 'San Francisco' continues even now to evoke dreams in the hearts and minds of people all over the world," he wrote on his website in 2002. "Though many of these people were alive when the record was first released, an increasing number of them were not even born then. Yet the same simple song touches them too."
Shortly after McKenzie hit the charts with "San Francisco (Be Sure to Wear Flowers in Your Hair)," he faded away from the music scene, moving to Joshua Tree in California before spending a decade in Virginia Beach, Va.
McKenzie revived his career in the 1980s. He co-wrote "Kokomo,'' which went on to become a No. 1 hit for The Beach Boys in 1988, and toured with The Mamas and the Papas in the 1990s.
Despite his illness, McKenzie continued to write. His last Facebook message featured a poem composed just days before his death, titled "The Final Ride."