This research investigates and describes an image search engine for digital history using deep learning technologies. It is part of the Engineering Historical Memory research, contributing to a multilingual and transcultural approach to decode-encode the treasure of human experience and transmit it to the next generation of world citizens. The engine provides a new way to search in online (historical) digital libraries using content-based image retrieval and makes linguistic metadata redundant. State-of-the-art deep learning methodologies in computer vision have been investigated and tested. These methodologies include both template-based matching and feature-based matching. A VGG16 Convolutional Neural Network based approach, called D2-Net, is concluded to provide the best basis. D2-Net is then further analyzed, improved, and optimized to run on a large dataset of more than 12k image combinations related to history, heritage, and art. The final implementation shows promising results with a precision of 0.96 and a recall of 0.44 on a challenging testing dataset. Future improvements include speed improvement and model training.