During the 1970s, she joined the Prairie Fire Organizing Committee and later went underground with a group accused of buying explosives to aid the independence movement in Puerto Rico.
[1][2] In 1981, she moved to Los Angeles and went underground as part of a militant group which used its white privilege to buy explosives to be used in freeing Fuerzas Armadas de Liberación Nacional Puertorriqueña (FALN) prisoner Oscar López Rivera.
[1][2][3] Block had a second child and lived underground with Marks in Pittsburgh until 1994, when the pair gave themselves up to the authorities in a negotiated settlement.
Block formed the California Coalition for Women Prisoners and wrote her memoir Arm the spirit: A woman's journey underground and back, which was published in 2009.
[4] Reviewing the book for Truthout, Dan Berger said it was "a nuanced and intimate portrayal of radical activism's far-reaching consequences.