The creation of structured digital libraries from paperbased archives is an area of growing demand in many scientific and cultural fields, and is not satisfied either by off-the-shelf OCR or commercial form-processing systems. This paper describes and evaluates a configurable archive construction system, which integrates document image pre-processing and analysis with text post-processing tools and a standard OCR package. The prototype system is currently being used in conjunction with the UK Natural History Museum to help convert more than 500,000 cards of Lepidoptera and Coleoptera to a searchable digital archive. Evaluation results are summarised for two datasets comprising over 5,000 cards selected from different parts of this database, and indicate that overall end-to-end word recognition rates of 70-90% are readily achievable for key data fields, subject to availability of suitable electronic dictionaries.