BEACON - Legendary American folk singer, social activist and Hudson valley resident Pete Seeger has died at age 94.

Seeger's grandson, Kitama Cahill-Jackson, says Seeger died Monday night of natural causes after being hospitalized for six days.

Seeger gained fame as a member of The Weavers, the quartet formed in 1948 and had hits such as "Goodnight Irene." The Dutchess County resident popularized the song "This Land Is Your Land," and is perhaps best known for co-writing "If I Had a Hammer" and "Where Have All the Flowers Gone?"

Along with his wife Toshi, Seeger founded the Hudson River Sloop Clearwater, Inc. in 1966, an organization whose mission is to protect the Hudson River and surrounding wetlands and waterways. He also founded Clearwater's Great Hudson River Revival Music Festival in Croton-on-Hudson.

He continued performing and recording for six decades afterward and was still an activist as recently as October 2011, when he marched in New York City as part of the Occupy Wall Street protests. He was onstage in January 2009 for a gala Washington concert two days before President Barack Obama was inaugurated.

Seeger was awarded numerous honors during his lifetime including the Grammy Lifetime Achievement Award in 1993, a Kennedy Center Honor in 1994, and he was inducted into the Rock and Roll Hall of Fame in 1996.

Greenburgh Town Supervisor Paul Feiner has suggested that the new Tappan Zee Bridge should be named after the singer.

Feiner says that Seeger fought to save the Hudson River from pollution and says drivers would be reminded to keep the river clean.

AP wires were used in this report