MacAdams was born in San Angelo, Texas and graduated from Princeton University in 1966. He is the author of a dozen books and tapes of poetry, and his poems have appeared in many anthologies. In 2001, he published his Birth of The Cool, a cultural history of the idea of cool.As a journalist, MacAdams has been a contributing editor of the L.A. Weekly and has written regularly on culture and ecology for Rolling Stone, Men’s Journal, L.A. Times, and Los Angeles Magazine.
As a political activist, MacAdams is a cofounder of Friends of The Los Angeles River (FoLAR) established in 1985 (and has served as Chair on their Board of Directors). FoLAR has been characterized by MacAdams as a "40 year art work" to bring the Los Angeles River back to life. In the years since, he has become the River’s most important and influential advocate. Among FoLAR’s many projects are an annual river clean-up, the "Gran Limpieza," which brings 2500 people down to the river to clean up every Spring; and an on-going series of conferences and planning workshops dealing with every aspect of the river. Two of its current major goals are to create a Los Angeles River Conservancy to oversee restoration of the river, and a River Watch program to improve the River’s water quality and target polluters
In 1991, MacAdams received the San Fernando Valley Audubon Society’s annual Conservation Award. The River: Books One, Two & Three, takes the Los Angeles River as its metaphor, weaving the story and song of the poet, activist and journalist as these three roles form the confluence which is the man.