When working with an archival collection, it is important to understand the difference between types of sources. While secondary sources collect material and present it through analysis or interpretation, primary sources are contemporary and first-hand accounts of original information.
Primary source documents can be a wide range of items. Here are a few that we hold in our collection:
| Primary | Secondary |
| Letter from Jonas Clark to G. Stanley Hall | Biography of Jonas Clark |
| Atlas of Worcester, 1900 | A History of the Canal District |
| Freshman beanies | Chronology of Clark History |
| Scientific study | Literature review |
| Photograph of students in Psychology classroom | Psychology textbook |