the harlan and hollingsworth office building is a historic office building located in wilmington, new castle county, delaware. it was completed in 1912, and stands on the corner of west st. and the wilmington rail viaduct. it is a three-story, detached, rectangular brick-faced building with two small rear wings in the colonial revival style. it features two large, decorated copper-faced bay windows projecting from each face of the right corner of the second story.