I am not sure which one you are thinking of. Maybe the Free Library of Philadelphia. They have a large collection. You can join if you are out of state but there is a fee.
This post may have some information for you:
or maybe check the wiki
USA Libraries that offer cards online or by mail
These libraries currently allow non-residents to obtain cards without appearing in person.
* The Free Library of Philadelphia ($35/yr)
* Fairfax County, VA ($27/year)
* Charlotte-Mecklenburg County, NC ($45/yr)
* New Orleans, LA ($50/yr)
* Orange County, FL ($125/yr)
* Brooklyn Public Library ($50/yr)