RefWorks and online references are both extremely helpful in their own rights, but you always have the most control when referencing the actual style guide.
SU Libraries has a copy in Ready Reference, meaning it is available at the Research Help Desk for quick reference. It cannot be checked out of the library, so it is more likely to be available for anyone who needs it.
ProQuest RefWorks is a citation management tool. It's a really good start to keep track of all the sources you need for your annotated bibliography and paper. It is only a start, however. You will need to double check all of your formatting against the Chicago Style Guide to make sure they are correct!
You can check out this guide for help or ask a librarian!