In the late 1920s, George Darrow of the USDA began tracking down reports of a large, reddish-purple berry that had been grown by a man named Rudolf Boysen in Napa, California. He enlisted the help of Walter Knott, a Southern California farmer known as something of a berry expert. Knott hadn't heard of the new berry, but agreed to help Darrow in his search.
The pair soon learned that Rudolf Boysen had abandoned his growing experiments several years earlier and sold his farm. Undaunted by this news, Darrow and Knott headed out to Boysen's old farm, where they found several frail vines surviving in a field choked with weeds. They transplanted the vines to Knott's farm where he nurtured them back to fruit-bearing health. Walter Knott began selling the berries at his farm stand in 1935 and soon noticed that people kept returning to buy the large tasty berries. When asked what they were called, Knott said, "Boysenberries". As their popularity grew, Mrs. Knott began making preserves which ultimately made Knott's Berry Farm in Buena Park, California world famous.
Citizens for boysenberry jam was mentioned in "Punky's Dilemma", a song by Simon & Garfunkel.