Pete Seeger, who helped create the modern American folk music movement, died on Monday at the age of 94.

NEW YORK CITY, NEW YORK UNITED STATES (VNR) -  Pete Seeger, who co-wrote enduring folk songs like "If I Had a Hammer" and in turn became a leading voice for social justice, died on Monday (January 27) at the age of 94.

Seeger died of natural causes at New York-Presbyterian Hospital, his record company, Appleseed Recordings, said.

Seeger was well known for his liberal politics, working as an environmentalist, protesting against wars from Vietnam to Iraq. He was sentenced to prison for refusing to testify to Congress about his time in the Communist Party.

In January 2009, Seeger performed at a concert marking Barack Obama's presidential inauguration.

He then celebrated his 90th birthday in May of that year with a concert in New York's Madison Square Garden that drew 15,000 spectators and performers, including Bruce Springsteen, John Mellencamp, Emmylou Harris, Arlo Guthrie,Joan Baez and Kris Kristofferson. Proceeds went an environmental group Seeger founded.

"Like a ripple that keeps going out from a pond, Mr. Seeger's music will keep going out all over the world spreading the message of non-violence and peace and justice and equality for all," Jim Musselman of Appleseed Recordings said in a statement.

Seeger and Woody Guthrie started the Almanac Singers in the early 1940s and in 1949 Seeger was a founding member of another key folk group, the Weavers. Those groups opened the way for Bob Dylan and another generation of folk music singer/songwriters in the 1960s and '70s.