Toshi Seeger, folk singer Pete Seeger's wife of 70 years and a close partner in his social and environmental activism, has died. She was 91.

Longtime family friend Thom Wolke confirmed that she died Tuesday night at the couple's home in Beacon in New York's Hudson Valley, about 65 miles north of New York City. The cause of death was not immediately known.

Never famous like her 94-year-old husband, friends say Toshi Seeger was an equal who perfectly complemented Pete Seeger's idealism.

"To understand Pete, you have to know Toshi," Wolke said. "They were the ultimate yin and yang. Where Pete was ... the artist, Toshi kept him grounded."

Toshi Aline Ohta Seeger was born in Germany to an American mother and a Japanese father and was brought to the United States as a baby. She met her future husband as a teenager in New York City when Pete Seeger performed at a square dance and he stayed after to dance.

Pete and Toshi Seeger were married July 20, 1943. The couple built their cabin in Beacon after World War II and have stayed on the high spot of land by the Hudson River ever since. The couple raised three children.

The singer recalls on the recently released spoken work CD "Pete Seeger: The Storm King" how his extraordinary wife raised their young family in the cabin initially without running water or electricity while he spent months on the road.

"I'd be away. She'd put one baby on her hip and the other tugging at her skirt and walk 150 yards down a steep slope into a ravine where there was a little brook of clear water and she got a pail and walked back with water to wash with and cook with," Seeger said.

Toshi Seeger was particularly active with the Hudson River Sloop Clearwater, an environmental group. Tao Rodriguez-Seeger said his grandmother was a pioneer in festival production who played a key role in Clearwater's annual festival.

"Without my grandmother, there would be no Pete Seeger the way people understand it," Rodriguez-Seeger said. "That's not an exaggeration. She kept everything working so that he could focus on the world-saving, civil rights, anti-nukes, Clearwater — all of the projects that my grandfather worked on."