In a review of Jim Powell’s first book, Thom Gunn praised his poetry for tapping “a subject matter that is endless and important . . . achieved in the poem, so we grasp it as we read.” Substrate gathers three new collections of Powell’s poetry, the work of a dozen years. These poems open inward windows on the world outward from indigenous habitat in Northern California. They include the past as an aspect of the present, and spirit as a dimension of the actual. The title poem summons twenty-five witnesses from oral and documentary history to focus through the lens of poetry an adult view, over their shoulders, of California history—a compound portrait or collage sampling the indelible strata that compose the cultural substrate of the region. Diverse in theme, stance, tone, genre, and form, the poems in this collection are characterized by lucidity and penetration, plainspoken intensity, compression, and depth.