According to the ATLA website:
The ATLA Reciprocal Borrowing Program creates an arrangement between participating North American ATLA Institutional Members to grant check-out privileges to each other’s patrons/students.
A patron/student walks into a participating library, shows proof of current enrollment at another participating library, and checks out materials based on the library’s local lending policies.
If you are a patron/student, find a participating library close to you (and their contact information) on this map.
For more information, please contact the library staff at 512-478-5212 or email@example.com.