In the 40-year history of the historic tax credit (HTC) program, certain building types have become perennial targets for rehabilitation. Mills, factories, office buildings, department stores and schools are often well suited for adaptive reuse, with floor plans and finishes that lend themselves to new uses and the use of HTCs. This article, the first in a recurring series identifying the opportunities and challenges of redeveloping different types of buildings, explores mills and factories, two of the most common building types rehabilitated using the HTC program.