Where can I find historical betas?

For historical betas use Bloomberg located in the Ford Library.
Type the company's ticker symbol, then hit the EQUITY key, then type BETA.

Go to CRSP on the library database page.
Click on CRSP
Select Indices and Deciles
Select Portfolio Assignments
Step One: Choose a Year-end Beta Assignment
Step Two: Choose a Date Range
Step Three: Enter a Ticker Symbol
Step Four: Choose Beta value (BETAV) and DATE
Submit your request