SLU's libraries subscribe to several sources for biographies. You may want to start with one of the biography databases listed here to find article-length biographies, which may include suggestions for additional sources.
Here is a list of databases that are useful for finding biographies.
For some notable people, you will also be able to find book-length biographies. Use the Library Catalog to search for a person's name.
If you need any help finding a biography, just ask a librarian!