Many academic and cultural institutions have digital collections with Creative Commons licensing or identify those items in the public domain. Make sure to check each institution's guidelines before using an image.
Can I use that image?
Any image created on or before 1927 should be available in the public domain and not restricted by copyright (meaning you can use the image without asking permission, attribution, or compensation).
Fair use allows you to use images without permission or compensation for a set of given circumstances including for educational purposes such as a PowerPoint presentation for class or in a research paper given to your professor. One important aspect to Fair Use for educational purposes is that the image will be seen by a limited audience (your professor or your classmates in class or submitted in TheSpring). If you are not using a Creative Commons or public domain image for a project that will be made available to the public, check Fair Use guidelines.