Most labor and migration studies classify migrants with limited formal education or credentials as "unskilled." Despite the value of migrants' work experiences and the substantial technical and interpersonal skills developed throughout their lives, the labor-market contributions of these migrants are often overlooked and their mobility pathways poorly understood. Skills of the "Unskilled" reports the findings of a five-year study that draws on research including interviews with 320 Mexican migrants and return migrants in North Carolina and Guanajuato, Mexico. The authors uncover these migrants' lifelong human capital and identify mobility pathways associated with the acquisition and transfer of skills across the migratory circuit, including reskilling, occupational mobility, job jumping, and entrepreneurship.